I have only built one so far, A long wheelbase recumbent low racer design. Since a bike of this type can cost from $1800-$5500, I knew I had to make my own. It is a fully functional test bed for different seat angles, crank distances, and heights. Making parts adjustable causes them to be much heavier, especially with a 225lb rider. The extra weight is mostly in the "artistic" seat design, all steel construction and over engineering. It is10lbs heavier than my 5 year old, aluminum, full suspension mountain bike which is also overengineered. Despite the weight, uphill performance is vastly improved and comfort is the greatest advantage. I don't even ride the aluminum bike anymore except on the street. 

 This bike was built from a used 26"mens 18 speed, a new 20" bmx, 3 chains, 2 McmasterCarr idlers, and various bits of steel tubing for a total cost of  $100. I get a lot of attention, especially from the kids on the Georgia Comet Trail and Chief Ladiga Trail in Alabama. I expect to build a foam core, carbon bike with aluminum hard points after I finish my wife's tadpole type(2 front-1 rear wheel), rear suspension trike.