I had the curling problem with my Makerbot Replicator, and after trying to fix problems with the build platform (twisting, uneven heating, etc.), I came to the conclusion that the curling problem would be best solved with a heated build chamber. I started to build a box to keep around the printer, but I never finished it. The Replicator 2 has an enclosed build chamber to keep the heat inside, as do many other 3D printers currently on the market, something that wasn't the case ten years ago. An enclosed, heated build chamber solves a lot of problems.

@holovision, if you want to build a box to put over your printer, let me know, I can modify the design I came up with and send you drawings.