Retrofit an FP2 riser to fit an FP1?

So if I get an FP-2 riser to retrofit to an FP-1, am I further ahead than making an FP-1 riser from scratch? I know the FP-2 riser does not extend out as far as the FP-1 riser does, I can live with that. If the dovetails match, then it must be better to get the more obtainable FP-2 riser and re-fit one gear on the lower side to match the FP-1 gear angle. Right?

DJ