I must be odd then. Either that or my bear paw hands just don’t jive with the small diameter bar.
Pronated grip, thumbs on top of the bar.
Thumbs should not be on top of bar as that’s not actually gripping the bar, if your goal is to challenge and improve grip. If your goal is to just get more chins done, then thumbs on top of bar is the way to go yes. In vid, you will see I got called on it which made it much more difficult.
I’ve always treated chin ups and pull ups as two different exercises. Chin ups being palms toward you, pull ups being palms away from you.
My goal is to be able to do 20 pull ups from a dead hang, no kipping etc.
I’ve been doing dead lifts too, and I have noticed an increase in grip strength.
They are, and you can see both being done in the vid. Issue is where the thumb is placed regardless of which type of chin up/pull up is being done.
Thumb over improves number of chins one can generally do on a thicker bar, thumb under (using a true grip) greatly reduces number of chins/pull ups, etc that can be done, but challenges grip, forearms, etc better.
So thumbs under on a thinner bar typically is easier for doing more reps?
Interestingly, I’ve always done chin ups thumbs under. All of the exercises I do are always thumbs under, with the exception of pull ups.
Lately, I’ve been doing weighted pull ups but I’m starting to do more wide grip pull ups. I can really feel those on the back and rear shoulder.
I find pull ups, like push ups, is one of those excersies where it pays to be shorter. 
A long range of motion doesn’t seem to help.
Thumbs over on a thicker bar makes pullups alot easier. Thumbs under on a skinny bar makes pullups much harder IMO.
The thin bar we have in the academy gym doesn’t have any sort of grip material. It isn’t even knurled, and it always feels like my hands are twisting on it when doing reps.
Thumbs over for pull ups feels like a more natural motion. If you were going to pull yourself over a wall or a similar obstacle, your hands would be in a similar position.
Thumbs under, regardless of bar width or grip = more difficult.
Most of what we grip, when we grip, is using the thumb to grip around the object (a persons wrist for example) so if grip strength is important to you, train using full grip. Again, depends on goals, sport, etc. and both types of grips can be incorporated as it makes sense.
Thumbs over bar = suicide grip that lots of guys use on the bench press?
All this talk about about thumbs under makes me think of the hook grip, which still hurts like a mother to my unaccustomed hands.
I see a lot of people using the thumbs over on the bench press and I’ve tried it. Didn’t really care for it. I felt like I had more control with a thumbs under grip.
Gaston Glock did years ago with the G20!
I used to have grip issues with my deadlift, did “Kroc” rows for a while, basically just cheat bent DB rows with the heaviest DB possible (125lbs), did a lot of heavy weighted chins as well. I would do all my warm up sets for deads with double overhand then do my main set with mixed grip. Do 445 pretty easily now raw, while before I was having trouble doing 365. I’ve used fatgrips but mostly just out of curiosity, haven’t incorporated them into my split. Would work well with the kroc rows if you could hold on to it for more than 1 rep
Yes well, never been a fan of the ergos of Glock’s that’s for sure. 
There’s a number of effective ways to incorporate thick handle/fatgripz training but sounds like you’re doing a damn fine job of it.
Will,
What do you think about the Captains of Crush grippers?
Alot of guys on brianenos.com seem to like them. Bob Vogel really likes using them and says they have improved his ability to control recoil.
Seams like the fatgrips are more for endurance and the CoC grippers are more for strength.
I have not used them, but I generally hear good feedback on it for grip strength. I can see that being another tool in the tool box. The fatgripz are more whole body oriented which I tend to like, vs highly isolated to just working the grip as the Captains of Crush grippers work, but I can see a value for sure for shooters.
All this talk about how to improve grip and forearm strength and no mention of timed heavy holds , farmers walk, or odd object grip training? Those exercises are excellent for adding strength to your grip. And as for the Captains of Crush, they make a excellent gripper and it will help to add some grip strength, but in my experience they are much better suited as a test of strength rather than a tool to build strength. Nothing beats holding something heavy to build strength in your grip.
Farmers walk with thick handled dumbells in vid I posted. I do farmers walk with fat gripz on a trap bar as a one way to improve grip and general conditioning. Farmers walk using thick handle anything and or with fatgripz is great bang for the buck exercise all around.
Don’t do any timed holds myself, but it’s another solid method that increases the suck factor real fast. 
Will have you tried the Tyler Grips http://www.tylergrip.com/ fatgrip type product? Was thinking about trying them.
Have not tried them. They make claims that the cone shape is superior than standard thick handle training, but I don’t see any real support for that per se.
Ordered a pair. Figured they were at least worth a try as much as I like the FatGripz. Pressure on my wrists/hands is a real problem for me with Reverse Grip BP. FatGripz didn’t help in that regard. Figure the taper of the Tyler might make them a little more comfortable. I plan on integrating the FatGripz/TylerGrip into as many exercises as possible on my next workout cycle. I’l take pics and compare the 2 SxS.