I have been test fitting my 1.9 wheels on the Capra and found the following:
1) All SSD 1.9 steel wheels will clear the Capra portal without any issues as the back of our steel wheels are completely clear:
2) SSD00142 1.9 Double Time wheels need a 3mm offset hub (SSD00194)
3) All other SSD 1.9 aluminum wheels fit over the portal housings.
However as we use M2.5 cap heads inside the back of the wheels the cap heads just just touch the outside face of the portal housings.
So there are a few simple ways to resolve this:
a) Use an offset hub, this is not really necessary
b) Use a slightly wider hex, I plan to make some ASAP
c) Replace the cap heads with M2.5 x 8mm button heads. This should be done one by one after the wheel is assembled with cap heads first to prevent cranking and stripping of the smaller button heads.
The fact that button heads solve the clearance issue shows that the extra clearance needed is small (~0.5mm).
1) All SSD 1.9 steel wheels will clear the Capra portal without any issues as the back of our steel wheels are completely clear:

2) SSD00142 1.9 Double Time wheels need a 3mm offset hub (SSD00194)
3) All other SSD 1.9 aluminum wheels fit over the portal housings.
However as we use M2.5 cap heads inside the back of the wheels the cap heads just just touch the outside face of the portal housings.

So there are a few simple ways to resolve this:
a) Use an offset hub, this is not really necessary
b) Use a slightly wider hex, I plan to make some ASAP
c) Replace the cap heads with M2.5 x 8mm button heads. This should be done one by one after the wheel is assembled with cap heads first to prevent cranking and stripping of the smaller button heads.
The fact that button heads solve the clearance issue shows that the extra clearance needed is small (~0.5mm).