Cheers guys - smashing a pint of IPA and having a play with the design of the siren bracket in CAD to see if I can use a 3D printed part and still tighten the rear upper engine bolt without crushing the 3D printed plastic material (PLA).
Current thinking is to recess an M10 washer within a recessed pocket and use an M10x25 washer under the nut to transmit the load. I’m sure there’s a better way but the beer is flowing ha ha..
Absolutely stunning work, James!
A thought about the plastic bracket: could you use a thin nut to hold the engine's bolt, then the plastic bracket, topped off with another thin nut?
This used to be how we fitted some of the front case-crash protection bars, back in the day...