Combing two 500w 405nm diodes to increase burning power

Hi,

I'm considering buying a MicroSlice kit, which is a miniature laser cutter/engraver that uses one 500mw 405nm laser to do the cutting, and a 3 element glass lens.

I'm interested in increasing the power of this by using two of these diodes and a PBS cube (Which I read about on another thread in this forum).

The effective focal point through the lens is 8.3mm, and without the lens the diodes focal length is 3.1mm.

My question is, how far away from the pbs cube are the lasers mounted, and how far away is the burning point from the pbs cube, the focal point of the standard diode?

Thanks,
Waka

BTW I'm new here, hi! :)