Achieving flat trim is not just about switching fins and moving weights, they will have some effect for sure, but real stuff lies within yourself. Assuming by shifting weights and wearing buoyant booties etc, you are able to achieve trim at 10m, how can you be sure you can do the same at 30m, considering your buoyant boots or wetsuit will lose buoyancy at 30m?
Key to good trim is first achieving good buoyancy control. From my very limited experience (especially limited these days),you carrying 3 weights with an alu backplate setup sounds a little excessive. Overweighting IMHO, creates many complications, stopping you from achieving good trim and freedom underwater.
A good way to fix this issue is not to spend more money on equipment but to sign up for a proper course. A good course may sound expensive but it will save you plenty of experimental gear purchase, frustration and add to your dive safety and enjoyment.
For your information, I wear an XXL size jet fins with steel spring straps and stainless steel buckles.. I think my trim is ok.