Hyper 9 20 Degree Engine Mounts & Shafts?

[Dazzler]

Can anyone give the reasons to why 20 degree engine mounts are available for the Hyper 9, and why there are different centre shafts which are to be used with the 20 deg. mounts.
Are these specifically for use with particular engines? Is there anywhere you can find reasons for the introduction of these option parts? I've tried scouring the net today with no joy... But here on Oople i'm sure i'll get some reasoning. Maybe a link to some info etc..