Dsk,
An OS 52 Surpass 4-stroke would be a great motor for your 4*40. The great thing about a 4-stroke is that it's got a bit more "omph". You can swing a bit larger prop which will give you a little more power. Plus 4-strokes use less fuel than a 2-stroke. You won't get all out screaming speed, but since this is your second plane you probably don't need that anyway. I've got an OS 52 4-stroke on my GP Slow Poke 40 and I love it. I think you're making a great choice here.

Hope this helps

Ken