Joe,
That's a good 'peace of mind' mod, but as short at that receiver is, it's plenty up to the task. That's not going to be a failure point no matter what you do. Well, maybe that's a bit strong, but if you bolt them on properly, they'd never fail. In fact, I had misgivings about the spar system for a while during the time I was building my first one. I figured it's just a hair over 1/8" thick and the wing was so big comparatively so it just looked too small. Same with the receiver. Well, after I thought about it, I realized that if it was ever going to be a failure point, it would have done so already--especially on some of those Olympus-powered birds that were 50+ pounds dry that I've seen fly. Finally, Kenny Falconer's crash was a study in what those spars will and won't do. Two 120's, and the plane was at full power and rolling fast as it hit (wing first). When we examined the remains, any shred of doubt about the spars was gone forever. It was astonishing to see what happened, but the gist of it was that even a devastating impact couldn't defeat the setup--let alone flight loads.
That engine you have in there is such a great combo. I built one with a 170 and it was nice. LIGHT!