I recently purchased and installed a low profile gas block to fit under a floating forearm. When I installed the gas tube, it when into the block very snug but went in by hand. When I inserted the roll pin, it was loose on the gas block. It tightened up as it went through the gas tube hole. The gas tube does not move in the block and the bolt cycles just fine by hand. Tube alignment is ok. But the holes in the gas block for that roll pin just look too big. I did have to use a drift punch to drive the pin through the tube. And yes, I verified I had the right sized pin.

Is this something I should be concerned about, or am I just sweating the small stuff. I have not shot this upper yet because I am waiting on some other parts to get in so I can finish my mods to the rifle.

I bet they would be happy to refund your money or exchange the block if it really bothers you.

Sounds like it's already secure.  I havn't seen it, but, I would be inclined to put a drop of red loctite on it and keep it.