Hi Nigel , I've fitted a '78 alloy Maico enduro tank , as favoured by Scheck . I had to remove the original front mount and bronze weld a new upstand onto the main spine . The top of the rear frame loops where they join the main spine also need a small mod. in order to accommodate the narrow tunnel . Tank front mounting cheeks need to be altered at the bottom to match the headstock . I'm using the Maico seat too . I don't know how things would work out with the std. BM seat ? An '80's Maico tank is a plastic affair which is a different shape to mine but I'm sure the mods. will be similar . Best of luck ,
Mike