just mocking up at the moment for the next incarnation of my old reliant van . how much ground clearance do you need to run for the sump on a middie ? i had the bike engines flush with the bottom of the chassis but might need to run with the sump a touch lower on the saab engine

as much as possible? seriously - I have 2.75 inches and I'm worried. I believe speed bumps are legally allowed to be 4 inches.

As long as you don't drive your wheels either side of those narrow bumps it shouldn't much of an issue as the wheels will lift the car.

In my Zero the chassis should be 100mm and the sump sits an inch lower, but not too worried as the sump is very near the axle line. Should be similar for your mid engine setup?

My engine is currently sitting on the rear subframe, does any one see this as a problem?

I could lower it and hence have the sump sticking out under the chassis, however, my rear sub frame design and engine choice currently means there is a cross brace section under the sump, so i would need to redesign this if the CG of the engine would cause significant handleing issues.