Originally Posted by PeterPS
Here is what an engineer at Meopta told me some time ago:
"The dioptric compensation between the eyes, nominally listed as +/- 3D, is bigger and minimum difference we measure is +/- 6D."
I know you need -4d, so you should be fine.
I just checked B1 8x32 and 7x42 and although there are no engravings indicating the available dioptres the wheel turns a very long distance indeed.