do you get any grounding issues with using two different psu's?
They're both grounded at the socket, so no. It's good practice to have them share a ground connection though.
It's pretty easy hack them together with just a little bit of wire. All you have to do is draw 1 wire (pin 14, green wire) from one ATX connector to the other (where the "on/off" signal is generated). The PSU knows to turn on when this wire's voltage goes to 0 (ground). The adapters also include a ground wire (black) which isn't strictly necessary, but does insure both PSUs are grounded correctly (safety thing, not strictly necessary). You can draw this wire as well since it's about a 2 minute job.