I'd be interested to read your thoughts about running dual 44s on the engine. I have a 61X with single 46, red pipe and milled head. From what my buddies tell me it'll be an arm ripper as it stands. All I need to complete the package is a b pipe and I am good to go. It'll be a stout engine for me.
I have a 650 X2 that is ported, A/M head, WC exhaust, 44 sbn, and it is a get up and go monster.
Good luck with the build!