While i was building the Wilson II I had already decided that I wanted an aluminium build-plate and lower support plate.
I originally was going to use 6mm for the lower and then 3mm for the upper but after getting them cut using the sizes from Martin’s drawing i found that the 6mm was to heavy and would cause the Y carriage to have momentum and this showed up in the prints. so it got swapped out for 3mm and it is perfect.
The top build plate has a 300w 12v Silicon pad heater from Keenovo (very fast at supplying and can do almost any shape size or wattage) which in turn is controlled by a DC to DC Solid state relay (very easy mod).
Total cost, well the only things I had to buy was the heated pad and the relay(Know someone who owns a fab shop that uses water jetting )