Hi Steve
When I altered the CVH sump for the engine I was going to use, it only needed 20 -25mm removing from the bottom.
You should be able to follow the general guide in the book
If you take 20mm from the sump, take the same amount from the pick up pipe.
If you look at the sump when the engine is bolted to the gearbox .... You'll notice that the sump is not a great deal lower than the bottom of the gearbox bell housing .... You'll not gain a huge advantage by removing too much sump
