Hi Aidan,
I think you would need this
http://www.bintel.com.au/Eyepieces-a...oductview.aspx
but always best to check with the guys selling the gear. adaptors / connectors etc drive me crazy. it may need this
http://www.bintel.com.au/Eyepieces-a...oductview.aspx rather than the one you chose, but again, best to ask them at Bintel.
As for coma, it will essentially be gone at F8 or near enough to it.
Tracking may become more of a problem with double the focal length and that is something to consider.
cheers,
rusty