The Manual states 13" between centres, but I've seen 12.9" mentioned also (no biggie!)
Ikons perform very well, and are well worth the investment.
I've got a pair of Falcon shocks ready to put on my proddy racer, but as I haven't built the bike yet I can't comment!
They build to order and aren't as expensive as you'd expect - depending on what your requirements are, of course.
They're still not cheap, though. It depends on what level of performance you require - Hagons are OK for a 'daily rider', and still make the correct type for the Commando.
1974 Commando Roadster
1964 650SS Cafe Racer project
Production Racer project in gestation
1975 Ducati 900ss x2
1976 Triumph Bonneville