Using all the supplied aluminium on the battery and fuel pump brackets my Dad got some more 2 mm flat bar from B&Q. He spaced the tank so it wouldn't hit the rear brake 'T' piece. Then he began to bend the flat bar giving a few mm gap for the rubber foam as it doesn compress that much.
With 2 brackets made he drilled 4 holes into the chassis. The chassis rails were then lined with foam to stop vibrations and wear.
The tank can then be bolted down with 4 M6 bolts with a standard nut, washers and a nyloc at the end.
To know how much fuel is in the tank we need a sensor with a float on the end to give tank level readings. With the unit supplied from MNR we found a location for the sender, checked the movement for the float and cut off any remaining metal.
Using the 38mm hole cutter we drilled through the tank at the front(the deepest section to give the most realistic fuel gauge ratings). 5 holes then need to be drilled to accomodate the rivnuts. These are basically threaded insterts so a bolt can be used in thin metals that can't be tapped. Only problem is you need a rivnut tool to attach them which is a bit of a pain as we don't have one and they're about £20-30 from specialists. To get around this we threaded a nut to our m5 bolt that would go in the rivnut. A load spreading washer was then put on and we screwed the assembly into the rivnut and pushed it into the hole. Using 2x8mm spanners we kept the bolt head steady with one spanner and then clockwise turned the lower nut about 3 times. The effect of this is that it pulls the shaft of the rivnut towards the inside of the tank to hold itself in place almost like a rivet.
The seal is then put on with some sealant, the sender can then be fitted and the 5xm5bolts tightened with some loctite.