Morning D....good to see you back in action.

IMO, shooting BIFs and static birds with a big lens.....a gimbal is paramount.

My Wimberley gimbal is on my big tripod 100% of the time and pretty much exclusively used w/my 500.

Using a gimbal isn't complicated D......'"perfectly balanced" is a relative term. People simply say removing your hands from the equipment and the combo doesn't flop forward or backward. But they don't mention if they've left any resistance on the pitch setting. I know when I was looking into a gimbal, I interpreted "perfectly balanced" as totally friction free. I have since learned, for me, perfectly balanced includes pitch friction on the gimbal.....this may have been obvious to some of the more experienced photogs, but it wasn't for me.

My setup is quick, set the tripod for height, place foot in the gimbal's tray tighten....after using your combo of the gimbal and camera/lens you will discover, approximately, where to place the foot in the gimbal's tray.......in the down moments of shooting my subjects, I will fine tune the foot's placement and resistance.

I like pitch resistance for 2 reasons; obviously decreases the chance of the equipment from flopping when you remove your hands and I like a bit of pitch resistance while in the act of shooting and tracking a BIF. BTW.....I use zero friction for rotation.

Zooming; Peety has a valid point, but I think you'll find that you will be at max zoom the majority of times for shooting birds. One of my cohorts, he shoots w/a 7D2 and the version one 100-400, is nearly 100% on full zoom while shooting and that includes photographing HBs in my backyard. Obviously, you will have to maintain awareness for this possible balance discrepancy.

Leveling; for me, this is a low priority, don't misunderstand, I try to set up closely to level. But when I'm shooting BIFs and birds perched, I'm seldom able to fill the frame and my pix need cropping in post processing.....this is where I straighten any line issues. E. G. yesterday I was photographing bald eagles and I was able to approach one eagle as close as I've ever been able to get w/out causing the bird some anxiety w/my presence. The photo still needed a lot of cropping.

Gimbal suggestion....I haven't use one, but another of my photog cohorts has one and hasn't expressed any concerns; http://www.tripodhead.com/products/s...patibility.cfm

A nice benefit of this, not just expense wise, but it will eliminate the need for mounting and dismounting your ball head when the user only has one tripod.

Good luck w/your decision D

Bill