Edgar Marsh's book Sailing Drifters has the drawings for a similar St Monance Fifie True Vine ML20. This is almost the same hull size although the mast sizes are slightly larger than those given for the Reaper. It might help in giving the general proportions though.
Foremast 65ft 6in overall, Diameter 22 to 9in , foreyard 31 ft, dia 8 to 4in.Mizzen 55ft, dia 15 to 8in, mizzen yard 25 ft 6in, dia 8 to 4in, mizzen boom 28ft, dia 9 to 7inBowsprit 46ft 6in, dia 19 to 8in.The yards have a double taper while the rest are single tapered. Hope this is of some help.
Jim