Check out the Hangar 9 PT-19 in another thread within RC-Universe. It's the adult/modern iteration of the smaller Cox PT-19 we all saw/flew as kids. It would use the .40 engine you already have (with the thottle locked open) and any 10X6 or 11X5 props you may already have laying around. It builds easily in one evening. It's as simple to assemble as any other H-9 RC sport ARF. Its street price is higher than the others at $120. But it contains everything the RC flyer would need to enter/re-enter the control line circle- and nothing the pilot does not need. It even has an excellent handle and 60 ft lines. Build it and set it up as you would any RC plane. Just tune the engine much richer at about 9,900 rpm on the ground. Stick with the small provided tank at first. Also, make sure the cg is not even 1mm more than the 2.5in from leading edge the instructions detail.

Another option could be the Super Clown from Brodak. www.brodak.com It is about the same size as a Flight Streak and would use the .25 engine. If you already purchased and handle and lines for a FS, you could use them with this plane as well. If not, then you will need to acquire the lines and handle and connectors. To keep things simple at first, you could leave the flaps off. Just, don't get side-tracked with this excellent site dedicated to c/l flight. Top Flight also has a model larger than their FS, the Tutor II ARF. This could also be considered for use with your .40 as a trainer. I thought it was out-of-production, but is still listed on their web site.

Just as you learned that, "There are no jerks in learning to fly RC", "There are no jerks in learning to fly control line". Movements should be smooth and small. Just as you avoided quick stick movements to full deflection while learning RC, don't jerk the lines to full up or down in c/l.

Good luck and enjoy entering the ring with the original park flyers. Also, there is no such thing as 2 or 3 mistakes high !