Yeah obviously roo mince isn't a staple but they loved it. They seem to prefer the boiled eggs when they are younger plus they are less messy. I vary the diet as much as possible and have previously kept them for years, however only recently got back into keeping herps.
Anyway here's what you have to look forward to Reptilefreak95 (in around 8 months time) its the one I got in June last yr. Hes on top of 2 of those concrete bessa blocks to give an idea of size and not impressed with his new bare enclosure while his hides are being finished off.
The sizes you mentioned that you might go up to, are roughly the size of hercules (don't steal his name
lol) new enclosure, it's 1500x800x700 and should do him for another 12 months.
Another little gem that have kept mine extremely happy is something a friend of mine Troy Martin told me about.
Take 2 floor tiles (not porcelain) and some heatcord, spread the heatcord evenly over the back of one tile with the plug hanging out long enough (I drill a hole into the side of the enclosure and run the cord through it before making the tile) and tape it all down using silver sarking tape, (the thin one with thread in it not the one with tar masters sells it in smaller rolls) make sure you press it into the grooves so its a bit like a coil and it spreads the heat evenly. Then attach the other tile on top of it and you have yourself a heat tile, i put them under a hide buried in the sand and they always choose that hide to sleep in overnight, has worked with every Spencers I have ever kept, never had any problems with them, their bellies are kept warm so they digest food quickly and always been active and keen feeders