Hard? No. But, time consuming; YES.

It's actually pretty simple. Just cut the covering off the bottom of the tail and install a piece of aircraft plywood. That's your mounting block.

There are several different ways to control the tailwheel. You can use one of the simple ones that has a wire which is epoxied into the rudder. Not very robust, but it works, and the Kadet SR isn't really all that heavy anyway.

You can also use a Klett or OhioRC tailwheel. Mount a couple of blind nuts to the plywood BEFORE you epoxy it in the tail. You can prefab the tailwheel assembly with bolts and blindnuts and then glue the whole thing into the tail section at once.

For a pushrod, you can run a small 2-56 nyrod back to the tailwheel and install a small servo (HS-81 or an HS 55) or any small servo. Install the servo in the fuselage and connect it to your rudder servo with a Y-harness or you can mix it into another port if you have a computer radio.

I've done this on more than one trainer. The extra servo adds only a tiny bit of weight, but you have absolutly positive tailwheel control. It's really a nice setup. Add a couple of small balsa braces in the fuselage to keep the 2-56 nyrod from flexing. Don't over build the system. You can build it light and strong with only a couple of pushrod braces and a light ply servo mount.

You will need to move your main gear forward. The center of the main wheels should be about even with the leading edge of the wings. Just add a 1/4" plywood block in the appropriate place and epoxy it in. Use some triangle stock for bracing here. Mount your gear with blind nuts and bolts.

Leave the original mount in place where the main gear was. This can serve as the rear mount for your floats or skis in the future. Just cover the bolt holes with a piece of monokote and you're all set for the floats when you need them.

The process for converting the plane to a taildragger is NOT HARD. It just takes a bit of planning and some time. You could probably do this modification in a weekend if you just take your time and dink around with it for a few hours here and there.

Good luck. Hope this helps.

Remember to BALANCE the plane after you make the modification.