From what I've heard, the power difference is not proportional to the weight difference. The OS .46 combo puts out great power for its weight. Another consideration is the fuel capacity and flight times. The OS .91 drinks fuel like a thirsty sailor and you would be hard pressed to get much more than 4 minutes of flight time on the fuel that it is designed to hold. That plane was designed for a .46 and the weight, wear and tear from increased vibration, flight loads, and limited fuel capacity might not be worth the extra performance of the larger engine. I try to stay close to the manufacturers suggestions as it is in their best interest that we succeed. All this is not to say that a little planning and re-engineering can't make it work like a dream, but is it worth it? That is where your personal preference comes in. What others have done and experienced is a good barometer of what you can expect.

Good luck on your decision, let us know how it turns out.
Anthony