Another thing you may want to consider: when you dive twin backmount, you can use V-weights which are between the cylinder and backplate.
I usually do not need any weights on a belt in drysuit when I use my twinset and I find it nice to not have any belt.
So if you can get the backplate to be about the correct weight, you can just use a couple of v-weights to either do small increments or use a tail-weight if you need to fix your trim.
Here is a tail weight, you attach it using the bottom bolt:
Tail Weight
Here is a v-weight, you put it in the middle section between the cylinder and plate:
V Weight
I usually do not need any weights on a belt in drysuit when I use my twinset and I find it nice to not have any belt.
So if you can get the backplate to be about the correct weight, you can just use a couple of v-weights to either do small increments or use a tail-weight if you need to fix your trim.
Here is a tail weight, you attach it using the bottom bolt:
Tail Weight
Here is a v-weight, you put it in the middle section between the cylinder and plate:
V Weight