My Ventura rack mount is exactly like Macca's.
When I line the mount holes of the alloy plate onto the subframe it put's the tail light mounting tangs right in the middle of where the Ventura rack crosses.
Here's a thought tho. My subframe is of the 3 mounting hole variety. The Tail unit is for the 4 hole type. Before I boutght it, Jeff from Monsterparts tried it on an old tail section of the 3 hole type that he had that had been chopped and the front 2 holes line up. Was going to use them and drill two hole in the sub frame cross plate for the rear two.
But now I'm thinking that "maybe" while the 2 front holes do line up from the 3 hole to the 4 hole type, they are actually in different positions on the 2 subframes. ie my subframe has the 2 front holes closer to the taillight than the 4 hole type does. So (again maybe) thats why a 4 hole mount plate sends the tabs too far forward on my bike.
In which case maybe I have to drill all 4 mount holes through my subframe rear plate as they all need to be in different positions to my exisiting mount holes...
Or forget trying to use a 4 hole tail on a 3 hole bike.
(God I just re-read that...does what I'm saying make sense to anyone?!?!?)