I am a big dude also... and I was wondering about this...
I played back in the 90s and right when I got out Redz packs were the bomb! So naturally... I sought one out when I came back...
I found them here:
Problem is it is just large enough... when it gets cold if I have to wear a heavy jacket it is a no go... I can wear it with 3 shirts... but a heavy jacket is too much and it comes off when running.
Oh, and I assume that because my body is big so is my head? I use an eflex and it seems to work well... plenty of coverage.
Let me know if you have questions.
Interested in other posts to hear other's suggestions... I know one day I will have to replace my current pack.