just thought I'd put my two cents worth in the pot as well. I am a full time taxidermist, and have witnessed a lot of the same results you guys have mentioned. I have some ideas that you may find usefull or interesting.
First off, a deer's skull and antlers are full of blood or moisture that will inevitibly dry out over a long period of time. What you do with it during the drying time will determine the end result. If you must maintain the original spread of the buck from the day it was killed, then you must take immediate action. A stick or board should be cut with notches on each end and put inside the rack. To maintain a certain spread you will have to stretch that rack out at least another inch or two. If you do this while the skull is intact you run very little risk of breaking the skull. It is when the skull has dried for a month or two, and you try to stretch it out that you run the risk of breaking it. Also if you cut the antlers off the skull, leaving the small portion in the middle to attach to the mannikin it will obviously break much easier than a full skull will.
Dry the rack with the stick in it for at least two months. Take it out and it will snap back to nearly the original measurements.
This is illegal if you plan on having the rack measured for Boone and Crocket, or Pope and Young. If you don't have a book buck, then don't worry, it is not wrong or illegal.
It's ok to want the original neck size on your mount, then why not the original antler spread on the rack?
Also with velvet antlers you will lose more inches than you will with hard horn bucks. I have done some comparisons with bucks that my guided clients, and some of my taxidermy customers have had me strip the velvet on. On a buck that grosses around 195" the buck will lose almost 6" in gross score by stripping the velvet. Just to illustrate the reason, figure that each measurement will drop by 2 eighths of an inch, and the tine measurements will sometimes drop by 3 eighths inch. Add those up and you get some serious shrinkage. The same thing occurs when the velvet dries. You will lose mass and tine length as the velvet dries out. You can freeze dry the antlers and maintain the mass, but again it is illegal if you want to place the buck in any of the books.
I know this is long, but I just thought you might find it interesting.
Just one more thing. As the skull plate dries out and shrinks it will pull the antler tips inward, so the rack will lose more spread. The further the tips are from the skull, the more it will move them. Point is, the bigger the antlers the more potential they have to shrink.
This is my personal view on this, and there may be more knowledgeable guys out there, so take it as my opinion only.
Thanks,
Travis Roundy