Giant seat bag use question

[Mike Brown]

So I've been thinking about moving to the frame/seat bag combo.  Here's my question:
Visually, it looks like the giganto-seat bags would take away the ability to get really behind the seat- I mean seat at solar plexus arse in some void above the rear tire behind the seat. 
Is this true? 
Does it bother you? 
I use this maneuver often, incluidng when bikepacking.  Part of what I love is riding my loaded bike down the same technical trails I do un-loaded.  I feel like I'd miss this, but curiousity/ desire to lose some pack weight has me thinking.

[AZTtripper]

Yep you can still get to the same riding position but you can't over fill the bag. I don't have the biggest bag but it is the smaller of the two made by the artist formerly know as Epic. I do feel the pack but it doesn't interfere with riding.

I had thought about the bigger one but went with the next size down for just the reason you are thinking. I find I can ride any trail loaded that I can unloaded. The limiting factor being my abilities/guts or lack there of. But it also depends on how far out I am some things I might try close to the road I wont in the back country.

I can get a lot into the bag; warm socks go in first then a light weight bottoms mid weight top a 32 deg down bag and my poncho/tarp.

I recently learned that I can't add the bivy sack not due to length but width it caused the pack to bulge out and hit the tire. Moved the bivy to the bar pack no more rubbing. You can sort of see in the pic how close it was.