Last night I finished (sort of- I have to permanently run the wiring in the bot) my replacement heated platform. This uses a thinner Al plate for faster heating, has 4-corner leveling using the RepRap method of M3 screws and ballpoint pen springs, and uses an air gap for insulation from the base.
It heats up quicker and seems to hold temp well, but it's actually a rush job, so I need to make a better one eventually.
JSC