I hear you on the fiberglass, I’m going to be fiberglassing a pull behind trailer in the next month and I’m dreading it.I keep on imagining building one myself from a basic tadpole design. Unfortunately I absolutely hate working with fibreglass (it's messy and I'm useless with it) and that rules out most forms of compound curves leaving me with a bottom tub of minimal steel frame and thin aluminium panelling with a need to keep the canopy to basic single plane curves. I'm thinking fibreglass tent poles and clear pvc sheet for the canopy with that in mind hinged at the front and clipped near the rear providing entry / exit. My last tadpole tipped the scales at just over 30kg with rear suspension and a fairly heavy seat. With some swaps to material and some redesign I hope I could hit 25kg without too much grief. Any enclosure would add to that minimum figure and would need to be made with a constant eye on material choice. Theres a few designs out there avoiding compound curves but those made from coroplast don't float my boat at all. Also many don't have any underside to the shell and that upsets my sense of completeness. The closest I've got is a few ideas in my head keeping the wheels outside any enclosure for both ease of build and weight. The tub and canopy could be thinner and therefore lighter by not extending to the wheels and by using a go-kart like steering column rather than underseat or side levers. I think I could keep the number of holes needed in the tub to a lower number by passing the front axle and steering under the tub It'd still tip the scales at more than most of us would want to pedal but some electricity could assist that. I haven't solved access with a steering column present and may need to design a form of QR for it - not an area to get wrong!