The 150% should be a sail you use when conditions are (and are likely to remain) moderate.
For all other cases, you should start with a 100% standard jib.
The reason is that a 150% will be overpowered in many conditions and once you furl it, your DS will sail poorly. They do better with the jib up. In (predictably) light airs, I bet you'll really benefit from having a larger jib, though.
There are larger sails that people use with furlers, but the ones that have been discussed here in the past where more like a code zero than a standard genua. One member here flies his on a furler mounted on a short sprit. It's flown ahead of the forestay, so he can raise a regular jib after furling his bigger sail. (Obviously there must be some furler that can handle his sail, but I don't know without reading the old post whether it's a full 150%).
Check out these threads: "
Doyle Universal Power Sail" (the link goes to a part of that thread that has pictures) and "
Another UPS".