Even with post removed they don't fit. I'll try two things before cutting receiver plate:
-Battery plates upside down (or removing lungs for NiMh)
-dremell as much material from receiver plates downside (so now only small pressure and no engagement is needed).
I won't cut posts anyway, so the lack of strength will make them far more breakable.
Finally, possibly some carbon plate+thumbscrews would be used to achieve the goal in the most aesthetically optimized manner.
Or with battery straps as TC if anything works