If you're a reasonably experienced pilot then there is nothing wrong with an LA .46 on a 45 inch 3.5 lb plane. It's a 12 oz engine incl. muffler. There are 25s that weigh that much. As the guy above says, it'll be sporty for sure! But it's not at all unreasonable. If you were going to use a 17 oz ball bearing .46 then it would be a different matter.

I don't know what it's like to transition from electric to glow. Throttle response will be different, the noise may be a distraction at first. If you have any doubts get a little experience with a glow powered trainer or maybe just get someone on a buddy box with you for the first flight.

Just so you know, some guys object to the "nitro" term. They were always "glow engines" until electrics and came along, and some will point out that the nitro is an additive that not everyone uses (but almost everyone does). Not an issue for me. Good luck, and welcome to the world of fuel, oil and airplane noise!

Jim