This was a special-order Radial Flyer in MAC Performance 54mm tube.  T' Radial Flyer is normally offered as a 3" or 4" kit, but I asked Mike for one usin' his 54mm tube.  At t' time o' this writing, this be t' only one in this size that exists. Blimey! I added t' that a 3D printed boat tail o' me own design, lendin' t' appearance o' t' Aero Pack boat tail motor retainer that t' larger ones are designed for.  This has a 29mm motor mount and a 36" parachute.