This how I get the equivalent of a Alpha transitions to work in X as it did in FCP 7
I have been using the alpha transitions supplied with FCP 7
Put your ‘outgoing’ shot on the Secondary
Put your ‘incoming’ shot on the Primary and overlap by, lets say 1 sec
Add the Wipe Matte on V3 at the start of the overlap and apply ‘Stencil Luma’
Select V3 and V2 and create a compound clip.
This gives you the transition only, governed by the wipe matte
Drop the ‘Clip’ (ie Fill) on the next storyline above the transition and the ‘Alpha Matte’ on top of that.
Apply ‘Stencil Luma’ to the Alpha Matte and make a compound clip of those two clips.
Should now have a transition as required!