I'll just add that trying to build a velomobile with no prior hands-on isn't necessarily a recipe for failure; but you can expect to build 3 or 4 of them before you have a practical machine that fits *most* of your design criteria. Or you can buy one that's already been through all those design steps. The guys who have successfully built them on
BROL are those who have owned several and copied those designs into their homebuilts. Or they are someone who has build a coroplast velo body around an existing trike.