I've never had a sump but may in the near future and was wondering what is the minimum overhead clearance needed for maintenance? If my upgrade plans go through i want the stand as close to the same height as my current stand which offer 24" internal height and can be tweaked to 26-27". I ould like to get a used 55 or 75 for the sump to help with costs and this would mean 6-7" of head room plus 3.5" between the horizontal 2x4s running from front to back.