Assuming we are comparing standard lenghts, what type of speeds are gained by going with an Imco Standard lower instead of a standard XR lower?

Using the same gear ratio and prop, NONE.

If you ar over 80mph, then you might see a small gain from the Imco nosecone design.

I have found a 1-2 mph difference between the standard XR lower and an IMCO lower on a couple of boats, both doing around 80 mph at the time.

At 90, the difference was drastic in both speed and handeling .. 4 mph, and a much more stable ride with the IMCO on my Heat.

Slip went down, speed went up.. handeling was better.

Just my observations,

Chris

+1 for 4 MPH above 90 with twins vs. XR