I should imagine that a Saito 150 is about the same size as a 120 which are widely fitted,just reduce the thickness of the nose so it should fit. Mine measures 3.25 inches between the doublers and I've had to file them out a bit at the firewall to accomodate the Du Bro Quiet Mount which I shall be fitting.

If space is a problem, why not just reduce the thickness of the nose doublers?