Right... should be able to answer some of these...
It's not too much of a pain to take the seat off the Dragster but it takes a fair bit of setting up to get it the way you want it so you may want to mark the position of the webbing in some way before you take the seat off. The weight of the seat is minimal.
A BF on a Cadkat rim weighs 6kg
The Dragster is about 1450mm long from the headstock to the rear axle without the tuning kit fitted... add either 100mm or 200mm depending on the extenders.
Not sure what the front end weighs but... if the complete buggy with BFs weighs 48.5kg, minus 18kg for the BFs, minus 24kg for the frame that leaves 6.5kg for whats left.
I've been taking the front end off to get it in the back of the car but its a bit of a pain to get back together at the beach. The headstock bolt goes through 2 plain washers, top and bottom yolks, the headstock, a brass washer and a nylon washer.