Hello. The Astrohog is on the heavy side if you build it from the Sig kit. I have built two. Both had Saito 82 four stroke engines. I also have an 80% size Astro hog which was built from a scaled down plan. It is quite light for its size and is prefect with a Saito 40 four stroke. A friend has a similar one flying with a 25 two stroke.

I think your Irvine 46 will be too small for the Hog if you build it from a kit.

The Sig Four Star series comes in 40, 60 and 120 sizes. I have all of them. My 40 size has a 62 Saito, my 60 has a 100 Saito and my 120 has a 150 Saito. I have previously built a Four Star 40 with a Super Tigre 40 and it flew quite well but it was faster than I wanted. I find the four strokes work best. Also, my Four Star 60, which now has a 100 in it, used to have a Saito 72 in it. It flew perfectly well with the 72 but is more fun with the 100.

Cheers

Mike in Australia