Sump baffles

[Mikee]

Hey, im upgrading from my current 50g to 90g with overflow. It will have a sump/refugium (36x12x18) ..i plan to go skimmer --> Return --> Refugium my question is with the baffles. I will be using 3 baffles after the skimmer 1" apart the 2nd baffle will be 1" off the base of the tank and the 4th baffle will be placed before the refugium on the other side. The 3 baffles will all be 10" H and the other baffle will be 13" H i will be placing 1-2" of sand in the refugium. As for the width im not sure how much of a gap i should leave between the the glass wall of the sump? i dont want it to be to tight..since the sump is 12"(305mm roughly) wide i was thinking about getting the glass cut 11 7/8" (302mm roughly) this would leave 1mm or 2 on each side in order to leave a gap so the fit isnt too tight does this all sound okay? Thanks.