ill say a few comments to get you thinking:
plan on running in light rain? consider where the roof ends, drips on gages, legs ect sucks.
i like the B the high point- for structural reasons around your head.
seat of the pants engineering might suggest a flat roof will pancake in a roll, instead of roll out of it.
think out the X;s and support the frame rails from spreading apart with proper cross bars. matts car is just about the best we have done with the least amount of dead tubes
