Tricopter size???!

[demands]

Help

My new frame is now partially assembled, but so far the arm length is ~75cm (~30"), waiting to be cut...
I have been trying to read as much as possible online, but almost all threads talk about quad, very few cover tri's...

So, how big should my (newbie) tri frame be? It's square CF tubes, once cut there's no going back, and i don't have alot of spare tubes
Different places mention dimensions in different ways, as "motor to motor", radius, diameter etc...
What about tri??

I "know" about pro's/con's for different sizes, I just don't know what's considered "big" vs. "small".
Arm length "CG to motor shaft" would be nice...
I think I'd like it in the "bigger" range, to make it stable and easier to fly. No acro in a while, maybe FPV...

Oh, and I have the following:
HK 18-20A SS ESC
FC 28-22, 1200kV motors
GWS EP 10x4.7 and 8x4 props (how does frame size affect prop selection, which props should I use?)

[Lapino]

If you look for a FPV tri then have a look at this: http://rcexplorer.se/projects/tricopter/tricopter.html
and this:http://rcexplorer.se/projects/TriV2/TriV2.html
he uses 40 and 50 cm motor to CG
that's what I've, too ...just as a T-tricopter^^

[demands]

Lucky me And thanks Lapino!
I actually cut the frame before you answered, and they're 45 cm motor to CG... Should be a good start (I can shorten them if needed in the future)...

//demands