The only solution is weight control. Weight limits both the max and min speeds 'all else being equal'. If you can build your Curare down to 6 lb it will be able to fly as slow as a trainer, quite comfortably. Given that you are using a .60 up front, it will also be able to accelerate quicker, and have a higher top speed than (say) an 8 lb example, 'all else being equal'. But it will still be a Curare, aerodynamically. The trick is getting that airframe weight down, some internal redesign will be required, and real careful wood selection. Best I have done with a Curare, built to the original (wood) specs is 6.75 lb with HP 61 and muffler, no pipe. Landing speed, with flaps, is pretty slow....
Evan, WB #12.