Looking at some pictures, the upper shroud is attached at the deck edge, but the lowers are well inboard on deck. From the shots I've seen the genoa is intended to be sheeted in between the shrouds. A "large" genoa would, of course, run into the spreaders so I suspect that this boat is not intended for any more than a 130/135% headsail.
Many boats are being designed these days with the idea of keeping the headsails smaller - easier handling, smaller inventory. I expect the rig is designed to be powerful enough in that configuration.
Trying to fly a 150 would probably need to be sheeted outside the shrouds, creating a wider sheeting angle and possibly harming poiinting ability.
But I don't know the boat other than having been on a 36i and seeing some pictures.....
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)