the MH would definately be to close to the water, and I would worry about it, at best, warping the plastic top to the biocube.

if you raised the MH, the hole you cut would need to get progressively larger and larger.

if I were you?

Have Ace (hobogato) build you a nice canopy that looks simlar to the current one, put an icecap fan it, a retrofit lighting kit like your looking at, and don't look back.

I just got my new canopy back from ace and did a test fitting on it, it's perfect. now i just need to seal the inside, and stain it and I am good as gold. (or good as oceanic cherry in this case. )