Some Good news!!
Tested with no lenses to see the raw output and:
The emitter does in fact appear to be the same as the 300mW.
The divergence is larger but not by much, I did manage to get a similar beam as the 300mW using my test lenses.
So likely a shorter FL lens will be perfect just to take into account the larger divergence of the 500mW diode.
At one meter I have like a 5mm x 0.Xmm line + some considerable length wings. Pretty much the same as the 300mW.
Need a bit more time to get some shots and am also going to test a few other shorter FL lenses.
Don't get too excited yet tho, am still testing and hope to get a few photos soon.
Andy