RE: SR-71 prop jet project
Vic, I'm thinking about it......a pair of Cyclon .15s would do a nice job on a medium size model. Or Cyclon .061s on a miniature. That long nose sure is awkward for a small model to aerodynamically counter balance. I've built similar planes [with lots of area in front of the CG] that just always were looking for an excuse to spin. A big challenge would be to "design out" what we know won't work well at small model flying speeds without loosing the look of the original. Vaccuuforming anything that isn't part of the wing itself might be a good way to keep the weight way down and the time consuming carpentry to a minimum.
The power situation....the most power for the least weight. That is why I think world class combat engines are hard to beat here, plus you can get a pair of .061s for less than $300. The fuel system is a slam dunk, a single high pressure bladder with a line coming out of each end, it can be set anywhere on the plane, like at the CG. A pair of Cyclons running in the mid 30s should give the plane a pretty cool sound to go along with it.