Duds' Flitzer Z-1R is a totally different machine from the 'standard' Z-21. It's based on the fully aerobatic, four-aileron Z-1S with mass and aerodynamically balanced controls which was designed initially for a French aerobatic pilot. A few further Z-1S types were built, in Germany and the UK - sadly the UK example (UL Power 97 hp.) was written-off a few years ago in a sharp runway excursion - no brakes on that one. It is intended that it will be rebuilt however.
The Z-1R was developed especially for the R2800 radial. Due to the relatively high weight (220 lbs basic) of the R2800, stagger was drastically reduced and the lower wing chord and span was increased to match that of the upper wing, providing greater spar depths and more wing area. Fuel capacity was substantially increased. Another Z-1R flew in France but the builder had no experience of relatively powerful, open cockpit biplanes and had also connected his pitot static system in reverse. Having no idea of the 'picture' he was looking for on approach and with no IAS he hit hard at close to Vs and started to cartwheel, breaking the starboard wingtip, but flew out of the situation.
He re-flew a circuit and made another hard landing but survived, only to write the aeroplane off later doing high speed tail-up runs and throttle slams, experiencing considerable precession due to the steep ground angle of the machine (it had a 2 metre propeller) while experimenting with brakes. He performed this exercise for about an hour, until inevitably, gaining in confidence he lost control and wrapped it up in a spectacular ground loop and somersault. It remained in the corner of a hangar at Abbeville for a while but has since been removed.
The new owner of the UK Z-1R, G-ZIRA, enjoys practising aerobatics with that machine but it is currently undergoing repairs at White Waltham following some gearbox issues. It is a superbly-built aeroplane and a credit to Duds' workmanship. Many other Flitzer development types are underway across the planet, including the Flitzer-Laird LC-1W, Stormcock, Meteor, Z-2 Schwalbe two-seater, which will be equipped with the 124 hp direct-drive Verner 7U radial, F.2 Tiger, F-4, etc.
May shop is crammed with parts of various Flitzer evolutions to the point where I need therapy! :0)