Hi Top_Gunn, I am also a really big fan of the LT-40. I have flown/instructed on at least 10 different ones, both ARF and kit built. Ihave always thought that they landed better than most trainers, nice and smooth. I also have never really had any issues with float at all...unless your approach is too fast.
Let me explain something I have noticed/learned in 16+ years of flying, and at least 12 years of instructing. Most people have troubles with landing because they are afraid to slow the airplane down. Many guys are deathly afraid of stalls, because they do not want the dreaded "tip stall" and crash, so they approach at too high of a speed and then try and force the plane on. This of course results in either porpoising down the runway, or floating into the tall grass at the end. Stalls are nothing to be afraid of, I practice them all the time, and I get my students to practice them as well. Get used to the feel of the airplane at slow speed, and to recognize an impending stall, and know what to do about it. This enables you to comfortably approach a bit slower and have better landings.
Another thing, and this is a "problem" with the Kadet LT-40, Senior, and Seniorita series of airplanes. They have a lower wing loading and do like to fly slower than most other trainers. Guys who are used to flying/instructing using faster airplanes such as the Eagle 2, Tiger Trainers, Nextars, etc will naturally fly the Kadets the same, not even realizing it. This again causes them to approach too fast and float too much. It really is simply a matter of learning the different flight characteristics in this case.
The other problem that I have seen that causes most guys to float too much on landing is the prop size. Typically, when you go into a hobby store and buy a .40, you will get a 10X6 prop to go with it. This maybe is fine for a faster sport model, but for a slow flying trainer, it is too much pitch. That extra pitch might be just enough that it will not let you slow down, couple that with a slightly high idle, and you have an airplane that doesn't want to come down. Remember, pitch gives you speed, and diameter gives you thrust. On a slow flying trainer type aircraft, there is a "top speed" that the airplane will fly. Sure you can always put bigger engines and steeper props, but the speed will hit a point that it no longer wants to go faster. So, why not prop accordingly. For example, on a few of the LT-40's I have flown, they were powered with .40 engines, so I had them use either an 11X5 or a 12X4. Contrary to popular belief, even 4" of pitch is enough to hit that "top speed" with an LT-40. The other advantage of a larger prop diameter is more drag when the throttle is at idle. This will also help reduce the float. For an OS .46, I would use a 12X4 or 5 as long as you have the prop clearance.
As far as clipping the wings, there is no way Iwould do that. You would eliminate what makes the LT-40 so nice of a trainer, the slow flight, and stability. Personally I would not use any spolieron mixing either, just one more thing to be trying to fiddle with at the most critical point in the flight. The less stuff you have to mess with on short final, the better. As my full size instructor used to say.......first priority is to FLYTHEPLANE, everything else can wait.
I like the LT-40 a lot, but it, like a lot of other trainers, dates from pre-buddy-box days, when the main goal in designing a trainer was stability. The idea seems to have been, if the student gets in trouble he can take his hands off the controls and hand the transmitter to the instructor. For that, you want a plane that doesn't do much of anything when you take your hands off the sticks (and a student who doesn't get into trouble near the ground). Now that we have trainer cords, a more-responsive plane seems to me to make more sense as a trainer.
The main goal in any trainer is stability, buddy box or not. More responsive airplanes for the most part make it harder to learn, because things just happen too fast. A student will get themselves into trouble so quickly that they don't even know what they did to get it there, and they have no time or ability to react properly. They will get stressed and try and right it themselves and overcontrol, making the situation much worse. Even with a buddy box, by the time the instructor has it, it may be too late. A good trainer should be slow, stable, and yes, nice and docile. Less responsive is better, it gives the student more time to react, correct, and fly. Less takeovers by the instructor also will help boost the confidence of the student.
My LT-40 has minimal elevator authority - definitely needs more (more, more - an echo)
Hi Seamus, can I make a quick suggestion. Try moving the CG back a bit at a time until it flies the way you like it. If you are comfortable flying on your own this should not be an issue.