Depends on the flow through the sump. You can see s few shots of mine here.
http://www.mbrk.com/viewtopic.php?t=419 ... sc&start=0
I've got about 500gph through mine with baffles about 2" apart, and thats plenty of room. Main things to consider would be,
1. Leave yourself enough room to silicone them in place.
2. Put your equipment in first, everything. Then mark your baffle spots with a sharpie marker.
I had a local glass shop cut mine and drill my holes.