Setting up cadet dynasty for Aurane Waters

I'm wanting to play a campaign as Aurane Waters but give him his own cadet dynasty. I edited the TGA files so one of those four custom CoAs (that include the Darkholme one, you know what ones I mean) had the pre-made Velaryon-esque CoA on the second cadet graphics file, and used cadet.11 so I could choose/find the right corresponding cadet house with that image, but it never worked. Nothing changed at all, and he just stayed Velaryon. I tried doing this before and after self-legitimising Aurane. But so far the only cadet event that works (that I've tried) is cadet.15, but that just gives me a randomised CoA and not an officially painted one. And 11 doesn't work after that either, nor does any other event that I've tried (the event windows will pop up, but clicking on any cadet options will change nothing).

Is there some vital component here that I'm totally neglecting to do in the files? It always used to work in previous versions so thought I'd reach out.