A couple of considerations to try before you make the mod:
1) Attach a 3rd sheet to the clew of your 150 genoa. When you sheet the sail, do so as you normally via the toe rail lead blocks. But then, with some creativity, you should be able to figure a way to use this 3rd sheet to "in-haul" the clew more towards the center line. On my 1980 Cherubini H36, with a 135 genoa, if I lead this 3rd line (say with the genoa on the starboard) against the aft side (without wrapping) of the starboard cabin top winch, then wrap around the port cabin top winch, I can in-haul the clew enough that the genoa is up against the shrouds. See if something llike this yields the improvement you are looking for. For me, I find that in-hauling helps, compared to the just the toe-rail, but not radically. Certainly not enough to motivate me to add a rail/cars to my deck next to the cabin side.
2) Much more significant for me was to re-cut the luff of my many season genoa to reduce the blown out belly. Before, when pointing best I could into the wind, the leeward tell-tales would break when the masthead wind direction fly was say 5-10 degrees outside of the masthead markers. After the sail recut, they break when fly is right over, or even just inside, the marker. This was a really noticeable improvement for up-wind performance. If you've got a sewing machine, and time, and enough space, and your genoa is old enough that you are game to experiment, can be done DIY for just a few $'s. This was my approach, but I'm sure that a real sail loft would have done much better!
Just some alternatives maybe to try before you proceed.