I thought I had mastered this years ago.....

I am using the top slide set over method and have produced a pile of metal shavings and still no accurate taper!!!!
I clamp the cross slide and lock the carriage travel, the top slide gibs are on the snug side and the tool seems to be perfectly on centre (tested by end facing)

The top slide angle is set by mounting a DTI on the tool post and indicating against a plain bar in the lathe. Taper angle is not the problem, what is the problem is that the tapers are barrel shaped.

I cannot get the tailstock up to support the end of the workpiece without fouling the the top slide handle, neither can I manage to get a good finish turning the top slide by hand!

Today will be a busy day but maybe this evening I will get to have another try paying particular attention to tool height.