My question is why wasnt the H frame option remove from the software. Continuing to have the H frame in the software would lead to some confusion .
David,I tried H with mine (under 3.1x) and it wasn't happy. X works fine. Don't forget there's a lot of other tuning to do...
The reason is the direction the prop turn: you can use the X mode but in that case you could experience yawing difficulty. To solve this we need to change the prop rotation direction specifically for H frames; therefore an H mode.
If your frame is perfectly rigid, you can fly an H frame with the X mode; otherwise choose the H mode.
There is quite a physics difference in H vs X frame. When the props swing over air, they scoop up air and when they swing over the struts, they dump the air. Put your hand below and you can feel the downward thrust streams.
One prop direction moves the thrust vectors further away from the CG (center-of-gravity) than another.
Similiar physics to the "P" factor in low wing tail dragger airplanes (like a P51 Mustang) that cause them to pull to the left while taxing as the ground blocks the air flow on the right side and dumps the air flow down the left side of the fusealage, causing the plane to pull left.
If you look at the actual X frame image in the wiki motor setup page you will notice that the CW and CCW prop directions are reversed.
This was problematic because for no clear reason you had to reverse motor directions for each mode and it was confusing and unnecessarily redundant.
Initially the H setup was put in to compensate for expected but not well understood frame flex issues.
Generally however it was found you really needed a low flex frame no matter how you built it and the two different motor rotational directions had no influence on the copters performance at all.
Basically a properly made H frame (either configuration) with symmetrical motor /prop placement and a central CG is exactly like an X frame so the whole X - H Frame concept was found totally redundant.
In the case of a Dead cat design where not only are side/side and front/back prop clearances different but also the copters mass is concentrated narrow but long in relation to the copter you do need to unlock the roll and pitch rate PIDs and adjust them separately.
Long story short, the separation of X and H frame served no functional purpose whatever.