I've noticed a bunch of people (mainly those who use 32-bit windows) to suffer from more and more lag due to the mod's file capacity. It seems that for them, all their 1G RAM gets filled up rapidly. Before you say 'Allocate more RAM to Minecraft', because I know you were, this might form a problem for those 32-bit computers, since Java doesn't let them. The mod itself, along with Optifine take up atleast 70% of that RAM, leaving the rest to loading games, chunks, etc... This might seem like an over-asked question, but that doesn't make it less true. Has 4.1+ been compressed?
Aside from that, I love this, keep up the work.