funny, I owned a JVS Claim Jumper back in the day too (1974 or 1975, I was like 15 or 16 years old). They were pretty cool looking back then. I used an HP 40 (with Octura Kool Klamp). Wish I had pictures. For what they were, those unique hydro's ran very well once set-up correctly. Although I could never seem to get consistent results. The hydro classes were quite mixed backed then (Wing Dings, Cobra's, Drag N' Fly's, etc.,...).
And, yes, they were a little awkward getting to run properly. I think part of the problem, back then, was that most hobby shops did'nt have extensive experience with rc boat set-up & configuration (mostly airplane guys then). The instructions in those fiberglass kits recommended using fixed, (hull-surface) mounted, aluminum "parallel" strut's of specific depths (.875in, 1.00in, .625in, .500in, .,... etc). When they should have used an adjustable out-drive (transom-mounted) strut configuration which would allow one to find that optimum drive depth/angle.
I can remember seeing Jern & Vern Schmidth ("JVS") testing their new hulls back in the day at Legg Lake, also racing in NAMBA Nat's at San Diego Model Yacht Pond. They sold their boats exclusively through Hobby Shack (and direct I believe) at the time. Would also see Hobby Shack President, Paul Bender, running a few JVS boats at Legg Lake.
My first [serious] rc boat was a JVS mono, with Veco .19 with Octura Kool Klamp. They did beautiful fibreglass hull and gel-coat fabrication. If I'm correct, I believe Jern & Vern were involved ion full-size race boats before they ventured into rc model boats.