For what it's worth, the 'book' specs for the Scooter with 1500cc VW engine ('BDWE has the 1600 I think?) were as follows: Empty weight 390 lb; MTOW 625 lb; Max level speed 69 kt; Max cruise 61 kt; Econ cruise 56 kt; Stall 30 kt; Max ROC at S/L 600 ft/min; T-O and landing runs 250 ft; No-reserves range (5 usg tank) 152 nm. I believe the prototype had Vespa brakes, so your plan to 'Mod' it isn't entirely inappropriate!