So your going to repair the 150? How did you remove the frame when you say cut do you mean brake apart or remove intact for replacement?
It was removed intact, I used a razor blade and a paint scraper to cut the silicone that holds it in place. Also what size is your 150 bottom replacement glass? where will you get your replacement glass and what type of glass will you use/need, tempered, non tempered?
The glass is the front panel out of the 75 that I cut apart 
Like I explained, the 75gal is 48L and 31H, which is big enough to replace the 48L X 24W bottom in the 150. The only reason I bought the 75 gallon tank was to dismantle and use the glass to fix the 150.
Also when you say overlapping the edges you mean on top of and flush with the outer glass panes right?
Correct
Are you starting the 150 soon or will it be a while, I'm interested in your success in removing that bottom which actually when you think about it in so far as stability is concerned with all four sides remaining glued the bottom panel seems to be the easiest to replace since the rest of the aquarium remains rock solid as a platform to work on. The only concern is that it remains square and the glass is cut precise. I cant imagine what a piece that size will cost let alone my piece 24X72 $$.
It is upside down on my porch and being worked on right now. I imagine the stability will be just fine.
Please let me know what you find out about your 150 repair, problems & solutions.
