running two freelwheels isnt the same as a freecoaster hub. a freecoaster allows you to ride backwards without pedaling, two freewheels would just half your engagment points. I think that tensile freewheel would fit on your hub (same threads anyway) but I get a little confused as to which way the tensile lockring screws on, one way is better for on the cranks and the other is better for hubs if I am correct, but I cant remember which (or if it even matters) What size cogs are you using now? snail cams are very good, they are snail shaped (obviously) the hub axle goes though a hole and the outer edge pushes against a bolt (usually screwed through the frame just behind the dropouts) as you turn the cam, the distance between the center and outer edge gets bigger pushing the wheel back. Snailcams have been out since the dawn of time, motorbikes used them, then monty started using them on their frames decades ago. why have you got the seal upsidedown in your headset? I guess if it doesnt rock and still spins then its ok, but it will let water and grit inside and the bearings will go crap quickly. frames do flex, thats why there are boosters around, give it a try, should make the brake better too. (ps, I thought JT's answers were perfectly good)