this is the right way to do the welding in the RX8!

[mocky]

yes and yes. I've found a way around the problem, there wasnt enough contact with the soldering iron and post so i found a small chisel tip so i could slot it between the posts and heatsink of the ESC. Left me a bit frustrated, but relieved it got done without any damage, I only wish the slot in the post was slight larger and more space from the heatsink.