Hello Dave and thanks for your email!
Good to see the creativity blossoms in North Wales!
The upper end of my front engine mounts incorporate the bushings from a Peugoet 205. This reduces the vibrations on the frame. As aluminium is quite sensitive to fatigue cracking, rubber bushings was chosen. The downside is that the exhaust system will get all the vibrations instead, which calls for a very flexible design of piping and mounts. I have sorted it out by now, but that was a lesson learned. The upper mounts were CNC-machined and welded against the frame.
I saw your sketch of the front engine mount. I would recommend you to avoid the "T-joint" between the horisontal tube and the both vertical tubes. This design is very susceptical to fatigue cracking. From the pictures it looks like you have excellent possibilities to use the existing upper mounting holes on the frame. You can bolt an alu-plate directly against the frame and use a rubber bushing between the alu-plate and the tubes going down to the front engine mounts. I have seen this solution on more than one Supermono. If you use rubber bushings too close to the engine you will increase "leverage" from the engine moving around, which will increase the forces to the rubbers, or even let the rear mount take all the stress. It's better to keep the rubbers further away from the engine to reduce the force on them. I'm not good at explaining this so I depend on you being equally creative when interpriting my english!
You asked about the tank. I used the stock RS250 alu gas tank, but cut it out and fabricated a new inner "shell". Little tricky with the air ducts coming straight through. The welding was done by a local TIG-wizard, but I have gained the possibility and training with the TIG myself nowadays. If you prefer to work with glassfibre, you can fabricate a dummy, and use a more square shaped fuel tank underneith.
Good luck and let me know if i can be of further assistance!
