dont know the unit your talking about, kinda sucks not being subjected to the same gear, but thems the breaks! why dont u want to modify>? it might be your only option cause u cant restrict flow, esspecially cause id imagine your have to modify it anyways with a
dsb so u dont suck sand in! but theres the problem i cant understand, what no baffle in this unit>?
as for the sealed overflows, ive not seen them completely sealed, i have seen a shelf, or removable shelf above them for jumpers & snails, but more to the point coverings are used to sheld agains light getting in the baffle for limiting algae growth, 2mm gap clearance is the least i would recommend just in case the overflow teeth become clogged & it can overflow over the spillway!
im flying blind without a visual que or knowledge of the product in question anyways, might have answered your question in part anyways
