EDIT 4/29/17: Not updating for 0.15 see link below for original that has been updated. I have a new different armor mod using uranium here https://mods.factorio.com/mods/Rhaane/Nuclear%20Fission%20Armor for 0.15
Modified jimmy_1283's Power Armor Mk3 found here - https://mods.factorio.com/mods/jimmy_1283/Power%20Armor%20MK3
Wanted a smaller upgrade as 20x20 seemed awefully large. Modified the recipe to require Power Armor Mk2 to craft and slightly lowered other requirements. New Grid is 12x12 which is 44% increase over Mk2 armor.
Using this on a private server group, tossing it out here incase other people liked the idea but felt it was just too over powered.