The tank and it's frame are definitely a challenge. A pair of larger (thicker) veins to accommodate the frame rails with two smaller inside and one on each outboard side would accomplish "the look."
Exhaust can be dumped through it with tight clearance if it's done in sheet metal?
What you've accomplished is very impressive considering how tight the space is in comparison to most cars. From another perspective it's quite spacious compared to F1 engineering.
Keep it fun!
