Okay on updating:
You download the update exe
here, connect the GSP1101 via usb and update it.
If you already made patches and want to keep them, backup your patches with X-Edit FIRST!
You also need the newer version of X-Edit with the new firmware, download
here. You can also restore your old patches with this.
To upload IRs to the GSP use
this utility.
There is a tool in the mustbebeta forums for uploading multiple IRs at once, called G.I.R.L. (GSP IR Loader?). If you're still experimenting with IRs that can save a lot of time
On 4CM:
I use the 4CM, guitar > GSP, RM4 in the loop and GSP output to poweramp.
Technically you could also use the RM4's series loop as a return point (so you'll have the tube buffered output
after the GSP), but then you have more cables, I don't think it's any different.
Things to look out for:
The GSP can handle a lot, but if you're having weird clipping your RM4 might be outputting too much volume.
I've had it keep clean on 11 o'clock for both modules and master volume, I think more than that will start clipping the return.
Depending on your poweramp/other effects config: if you're getting a low buzz, switch the ground lift on the back of the RM4.
I'll try and think of some tips and tricks ..