Sharon Saare Trees vs. Stubben Trees

[bill barker <bcbarker@earthlink.net>]

We have two horses that fit a Sharon Saare size B tree.  Now my husband
wants to get a Stubben (the Saare is my saddle) and we are trying to
determine what size tree they need.  He has a Stubben Survival 19" on
trial, with a 31.5 tree and when he sits it on the horse, it has a 2"
drop between the pommel and cantle, instead of the recommended 1" drop. 
Does anyone know the correlation between the two sizes of trees?

Thanks,
Carol Barker
Central Region