i build a lot of fins in moulds. just made a shim for a normal mould to create asy fins. mixed results. trying different things. some very successful results during testing. fins are faster AND have more grip.
main issue is reducing the amount of work / steps in making assy fins. as well as standardisation in design and process.
I know. I prefer free / contra deals as eventually they get included with a board sale and I run out (like I have now) I also may reshape refoil or rebox/toe so plastic annoys me