Ok, warm-ups seem to be a recurring topic. Whatever your warm-up is aside, I've been doing mine (including scales and arpeggios etc.) on the single F I just purchased. I have noticed that the clarity on my top end once I switch to the double is much improved. I don't know what it is, other than I have to be more accurate in the high end of the F (and maybe that is it) but seems to be better than on my main horn. And, trying it out just on the F side of the Paxman doesn't do the same. Maybe the lightness of the instrument and its sensitivity is also a factor. Thoughts? Has anyone else noticed this?

Phred,
Yes. There are several top end teachers in Los Angeles that request their students to warm up only on the F side of their horns, they also ask them to do their exercises on F horn ( including Kopprasch) first before doing them on the double or triple horns.

It will increase your subtleness and accuracy.

Your observation about the single F horn is also true. Most double horns have compromised leadpipe made to work well on both sides of the instrument. If you had a longer leadpipe it would work better on the F side and less well on the Bb. If your leadpipe was shorter it would work better on the Bb and less well on the F. With the single horn the maker can make the leadpipe match the tapers and valve lengths perfectly making things better and easier.

Thanks for the confirmation of my observations. The F I got is a Carl Geyer. I think I've spouted enough about it being better than any other single F I've played, and it needs work done. The lead pipe is very long and the only section that is straight is the tuning slide. So I'm sure that the longer taper has a lot to do with the subtle attack I can use on the high end. Again, thanks.