I have a maxima in my 75g, but I have only had it for about 8 months. It has grown in that time, but my bigger issue is my red cap monti that I need to keep trimmed to prevent shadowing it. That grew froma frag the size of a quarter to ~10"x10"x6" tall in 2 years, and that is with multiple prunings.
My concern with putting a clam high in the tank is whether it would outgrow the support structure over time.
Kim