no experience with sids but cotic’s can run fine with rigid forks (the simple was first pictured with carbon rigid forks) which would have an axle to crown height of 440mm
i’m guessing a sagged SID would run around 430mm, but at full travel may feel too low – unless you don’t mind running them a little harder
i’ve always run my soul with longer forks (110mm ronin’s, 120mm marzocchics, 120mm minutes, and now 120mm rebas), and at full travel (i.e. assuming you never get the last 20mm out of them like me) they would drop to around 400mm (AC height) – a sid would be a good 30mm lower
looks that you are building a HT around your Sid’s to me – how about
try them first with the sids first (costs nothing), or
try a rigid fork (cheaper than a new suspension fork), or
buy a 100mm fork (cheaper than a new frame)?