Xgeek,
Wish I had more time to run some similar tests along side you on the "what's my weak link" range analysis. I have various combinations of the IRC 250mW, IRC 600mW, 2D and 3D gimbals (including v1.0 and v1.1), presence/absence of gimbal interference board, and presence/absence of GroundStation air unit. On the ground I currently have a Duo, with good helical, patch, and CP antennas, feeding Fatshark goggles, Lilliput screen, and now DVR.
All I can say at the moment is that my older P2 with 250mW vTx, v1.0 gimbal, and no GS (and older 3.something firmware) has almost double the control range of my newer P2 with the 600mW vTx, v1.1 gimbal, and GS onboard (though currently powered off) and recently the v3.04 firmware. (The GS when I first installed it had immediate impact on vTx signal quality, so I powered it off and taped the antennae away, assuming they were a garage band at the symphony, noise wise.) I am starting to suspect that the 600mW vTx may be hurting my 2.4GHz control signal at distance. The newer P2 flirts with FS/RTH substantially sooner than the older P2.
In terms of pure FPV range, last night I got 2.5km on two separate runs with the newer P2 + 600mW vTx. Very good video most/all the way. I am gradually learning best antenna placement on the P2, and what the brown-out / black-out orientations are on the turn-around several km out. Second distance run last night instead of turning around I flew ATTI backward (P2 vTx antenna facing me) until I got below 2km, then turned for home. Not crazy about looking where I was, not where I am going, even at decent altitude. On the older P2, I've hit 4km once, and >3.5km several times.
What firmware version are you using? Given the recent findings on v3.04 horizontal speed limits, I am leaving my older P2 firmware as is for the time being. I am starting to wonder if Manual mode is in my future re distance runs.
Kelly