I purchased the Senior for my wife and I would like to install a Saito .72 . I wanted to mount the motor at 90 degree's, so that the exhaust exits underneath. Is this a wise thing to consider? Is there any other options? Any help is appreciated!!!

Just built one for some friends. I installed their old old ST 40. It flies very well kind of like a powered balloon. I think mounting the engine on the side would work fairly well. I don't see anything that would make it too hard to do. I think the engine would run better on it's side.

PLJ;
As for mounting the Saito at 90 degrees there is only one problem. Centering the engine for the Cowl, to allow the exhaust to deflect properly. As you've noticed your tank location on the senior is fairly high. Your Thrust line is fairly high as well. Having enough room for the exhaust to deflect outside the cowl won't be a problem. But removing the cowl for maintenance may be! Without butchering the cowl to much. For Balance purposes the engine will have to be a little more forward than recommended. Balance point set at 4" or right on the spar works just fine and there is no weight added/Battery under the Tank shelf. With the Saito 72 the Senior will jump off the ground, so be ready for it.

If and when I ever do another one even one of the Senior kit's on the shelf. I'd probably go with a split cowl, as this will allow maintenance to the engine with ease. Then an inverted FourStroke could be installed with only the needle and exhaust protruding. As I've done on 1/4 scale CAPS (90 deg enclosed)and (Inverted) engine for Mustangs as on many others. I've always hated even cutting a small hole in a good looking cowl, so I look for alternatives to not cutting it up.

Hope this helps

I have one with an OS 65 LA and a 12 x 6 prop.

If you put an engine of that size on this plane, you want to think about changing the decalage (sp?) (i.e., the relative angle of the wing to the horizontal stabilizer). On my plane we see a lot of ballooning whenever power is added. If you raise the rear edge of the wing, or the front edge of the horizontal stab, you won't see the same effect on yours (I raised the wing trailing edge about 1/8th inch and it helped).

Who said anything about ballooning?

The Senior is an excellent flying aircraft. As you mentioned the right engine! Balance without added balast is the key to a light aircraft with years of use ahead. The Saito 72 weighs 16.5910 Oz's, the ASP 65 weigh's 23.125 Oz's, OS 91 weighs 24.250 Oz. (These are 4 Stroke)

Your 2 stroke: OS 65 LA weighs 18.9 Oz's. With the weight difference you would have had to add wieght.

There is way's to set it up with a lighter motor without using balast. But that would require a C-cell Rcvr pack under the tank and using mini BB servo's on the control surfaces (i.e. Hitec 225BB style servo's) Instead of full size servo's and a larger weight disp Engine. With the size of the control surfaces on this aircraft. I personally wouldn't want to trust a recovery to something that small.

Wow! a .65 on that thing. It flies well with a .40. I did have to add a bit of nose weight with the .40 to get it to balance.

A 65 is definitely too big, but it was left over from my sons last aircraft and so we avoided buying a new engine. We just limit the travel on the servo to limit the power.

By the way, this aircraft is superb. My son has been flying for a few years, and he's my instructor. With his help I was able to solo the Kadet (this morning) after just three weekends of practice (about 15 flights total). This thing flies like a big powered glider. It is very slow in the pattern, and that gives a student time to think about what is happening. It's probably a bigger step up to a second aircraft that flies faster than if you started with one of the smaller 40 size trainers, but that's OK. I suspect that soloing more quickly would keep more new folks in the sport. In any event, if your're new to RC and want to fly on your own quickly, the Sig Kadet is a great way to start.

It was just to much trouble to mount it at 90 degrees. Maybe if I had kit built it I would of planned it in advance. The Saito .72 seems to fit fine and I mounted it as far forward as possible for CG purposes. Thanks for the suggestions.