Skara

I've done it on cheap chinese buckles to make them work with Nexus Fastex ones. I used a dremel but a file is probably better to make sure you take too much off. Buckles are cheap af though from places like Contact Left etc so replacing isn't the end of the world.

Male Pentagon to female Helikon.

There is that little tab on the male that doesn't let it clip properly (one on each side)

Male Helikon to female Pentagon.

In this case the male is just a hair (less than half a millimetre) too short, I was thinking about shaving enough material from the female to let it clip in (will further secure everything with other materials too).

I don't think that those 2 mods will prevent me from clipping the 2 Pentagon parts together.

I will order more ITW repair buckles just in case something goes horribly wrong..

Condor male to Helikon female.

Here the male has 6 tabs, 2 on each "long" side and one each "short" one. I'll mod these as well.