Hello Weiselk,
My SP-10 MKIIA comes with two original armboards, one for the EPA-100 and the other for an SME. I have an SME/Oracle 345 which is essentially a 309 and it does fit, although the cartridge alignment remains a little off. I think a 10-inch or longer tonearm should fare much better.
Thanks Weisselk for your input and tip on OMA boards.