TubeNet

I have a Conn 28K sousaphone which plays wonderfully, except it is a bit sharp. The neck is very long and is very uncomfortable for me to play. I need 2 tuning bits that have large angles to get the mouthpiece to my mouth. I'm only 5'7" so maybe I'm shorter than most players. Anyway, I tried replacing the neck with a modern neck and that was about an inch shorter (less tall). It did help the sharpness, but I would like more to add to comfort and to lower the pitch a bit more. I was thinking of modifying the height of the original neck to cut out about 2 inches. That should meet my comfort needs and allow better tuning. So, any comments on this idea? Is there a different neck available that I could use to solve this problem? Any guidance on how or how not to do this modification?

I don't know of any 'off-the-shelf' optional necks but I've built several shorter necks starting with the standard tube.... expanding the large slightly to fit the receiver of the lower mouthpipe and trimming the small end before adding the mouthpiece receiver.

You didn't mention if the sharpness can be overcome with the main slide.

Thank you for the rapid replays. First, the main tuning slide is all the way in. When I wrote sharpness, I miss wrote. The horn plays flat and I need to shorten something to get it to play 440 and hopefully get a little room for temperature adjustment. The about 1 inch shorter new neck is better and just gets me to 440. If I take 2" off the old neck it should be about right for my comfort and should give me the tuning range I need. I'll start with the old neck and see how it goes, holding Allied filled with pitch option open. I have a friend who is a tech who will make the modifications. I will propose both solutions and let him decide which is best.