@Nan.roti did you mount your heaters at 45° in the back or keep them vertical?
I’m running the BRS units (10.25”), and unless I angle them at 45°, I have to raise my skimmer chamber above 7”. I wanted to keep it at 7” to avoid raising the skimmer.
I could raise the skimmer chamber to 10” to cover vertical heaters but concerned on how much drained down there would be because I only have 3” left in the sump
Otherwise I may just move them into the filter chamber where they can sit horizontal at the bottom and avoid the ReefMat entirely.