I need to try to use a 55x or a 50x on a HD-250 u is it possible with the 1/3 to 2/3 adapter or what other issues are their ?

Are you wanting to use a box lens or do you just need the long focal length?

If you're using a box lens, the 1/3" to 2/3" converter should work just fine, realizing that the lens will now have a magnification factor of somewhere in the neighbourhood of 1.5x (which would help your telephoto but hinder your "wide" angle).

If you just need long telephoto, you may want to look at the 35mm dSLR lens adaptors that allow mounting of 35mm (non ciné) still camera lenses. Mike Tapa (MTF Services) makes them for Nikon lenses.

Mike Tapa (MTF Services) makes them for Nikon lenses.

Mike also makes a very good 2/3" to 1/3" adapter, which I actually like better than Fujinon's ACM-17.

I would like to put a box lens but dont need to I am using it for a foh camera appox 125' from stage and need a head to toe shot ?

For these jobs I used the 18x4.2BERM (with 2X extender)
125 ft away will shoot an image of about H=3 ft at 152mm