See below…
i don’t think i’ve ever had a handguard be perfectly centered
Just takes a little tweaking, I have the DD FSPM. Using a piece that clamps onto the rails works to help align it. Use the carry handle or a sight that will fit across the gap from the receiver to the rail your installing. That is if you have a flat top receiver.
You can use a carry handle (half mounted on receiver and rail) to help center it while you tighten it down. I tend to just hold the rail and receiver between my fingers (while pulling up) and tighten down one of the screws to hold it in place. Then I tighten another screw and adjust the first screws tension if the rail moved at all.
C4
I used a carry handle to align the handguard while it was tightened.
Ya, that’s not really going to do anything.
C4
Just got back from the range. It appears the rail alignment may not be the biggest problem. I had to adjust the rear sight (Danaiel Defense) almost all of the way to the left side to get the sights aligned. When looking at the FSB from the rear, it appears to be slightly canted to the left which would explain the problem. When I took it off to install the DD Lite Rail, I used a Brownells bench block and made sure to remove the taper pins from the right direction as well as install them back in the right direction. With the taper pin attachment scenario, I don’t see how I could have mis-installed the FSB.
Any suggestions? 
I will give this a try. I would have thought the machined surfaces of the DD barrel nut would have forced the rail and rail locking ring surfaces at a perpindicular arrangment to the barrel nut.
First, make sure that the taper pins were returned to their orig position.
Then (with the receiver in the block) take a rubber hammer (or something similar) and give the FSB a whack the direction it needs to go.
If that freaks you out, remove the taper pins. Have a friend try and hold the FSB square are you drive the pins back in (receiver needs to be in a block). I do this by myself a lot, but takes skill and practice. 
C4
Grant:
Thanks for the recommendation! I assume you are saying to tap on the FSB with the taper pins driven in tight? Should I get new taper pins and install them or keep the old ones?
Drive the old taper pins in (to their orig position) and then smack the FSB.
No need to install new taper pins.
C4
Does the process bend the taper pins to allow alignment?
No.
C4
Grant, tried both of your suggestions to no avail. With the taper pins out, the fsb was aligned and clamped via another vice along with the receiver in a receiver block on another vice. When the tape pins are driven back in, they pull the FSB back to its original position. Short of heating up and bending the FSB (I’d rather not) I see no other way of aligning it except for possibly re-cutting the taper pin holes.
Did you hit it like a man or a little girl?
C4
Hit it VERY hard. What are we trying to do here, bend the FSB?
You cannot bend your FSB.
C4
OK…then what part moves when we we hit the FSB with the hammer?
Well you could hit it hard enough to bury the barrel extension alignment pin into the receiver.
To date, I have not been able to do this.
So, we are rotating the FSB around on the barrel.
C4
let me try to summarize what i think grant is getting at, and my own observations and experiences…
canted FSBs are caused by two things- either the FSB was installed canted, or the index pin slot in the upper receiver has been mashed during barrel nut installation. since your FSB is canted to the left, that indicates it’s more likely that you probably mashed it while torquing on the Lite barrel nut- they get more torque than other nuts, as you’ll recall.
to fix either problem, you need to re-index the barrel. this can be done by beating on the barrel or adding or subtracting material from the index slot. you can probably fix your problem by loosening up the barrel nut just enough to twis the barrel back into correct index, and then wrenching on the FSB counter-clockwise while torquing the barrel nut back down… two people helps, but you don’t want to twist on the FSB/barrel too hard, or you’ll just mash the index slot on the other side, making the problem even worse.
beating on the FSB is an attempt to either move the barrel index pin back into place, or actually mash the index slot (in the even the FSB was installed crooked)… if you can’t get it by beating on it, i suggest trying the above technique. a pipe-wrench works great, just make sure you wrap the FSB in a wash cloth or towel.