Hi Randy,
Well I see your html does not show up in my reply so I guess I'll have to try to remember my points rather than reply directly to your text. Darn technology 
First, won't the melamine from HD be 49" wide? I'm sure it is and I think it would be easier if the original poster stuck with 49" sections so he or she can limit themselves to cross-cuts for the long pieces.
Much easier, IMO.
Another point is that with an diurnal lizard lighting is a concern. If he has the sides fit outside of the bottom lip, bottom, top, and back panel then he'll have 49" inside of the cage to fit 4' light fixtures - very useful for lizards.
With the side panels spanning between the top and floor 1.5" will be lost from the inside of the cage. Even if the melamine is 49" wide there will only be 47.5" left inside of the cage.
Another advantage of this is that if glass track is used it will stop against the side panels rather than overlap them. This will make the cage more secure for all the annoying insects that will need to be contained in the cage.
Hope I got my points straight. Not having the text and diagram in my reply made it tough to double check my thoughts.
Otherwise, I like your plans. I need to learn whatever software it is you use.
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Current snakes:
1.1 Gonyosoma oxycephala - (Silver/Yellow)
3.4 Gonyosoma oxycephala - (Green)
2.1 Gonyosoma janseni - (Black)