Fleece Filter Roller & water height?

[VG30DE-TT]

I'm planning to build a new DIY sump and I'm thinking hard about incorporating and roller mat. Do they run completely out of the water level? or are they partially submerged? I am also building a new stand, so height is limited but I could build +/- 2" if it is required.

 

[blaxsun]

They are semi-submerged. They usually hang off the side of the sump.