Back in about 1988 a freind and myself bought a couple of fibre glass Arrows and powered them with Irvine 61re's with MK retracts.
The kit was a local "knock off" and came with foam cores. I also got a copy of the original plans, instead of the foam core tail plane, I made a built up one from the plan as a one piece unit.
Mine required a lot of lead in the nose to ballance, so keep the tail end light, it was my first pattern model and was a fantastic rolling model, oftern thought of doing a light one with fixed gear and a sports motor just to re-live the old days, good luck. Matt