OK, the real issue is the center hole in the backplate. The center hole in TT backplates is 3/8th". The DLE uses a 10mm diameter crankshaft extension, which requires reaming the center hole to fit the larger crankshaft extension. This is not something you want to try doing with a drill press at home. The hole must be perfectly centered or you're in real trouble. TT provides a backplate modification service, they will properly ream the center hole and drill the 4 bolt holes for a fee of $9.50
Now, to the issue of the 10-32 spinner bolt and the M5 threads in the crankshaft extension. Last night I didn't realize you could use the 10-32 TT spinner bolt in an M5 thread. A bit of a loose fit, but perfectly acceptable for this application, as the torque used on the spinner bolt is quite low.
So, there's two ways to mount the TT spinners on the DLE 30. Have the backplate modification done, or as I suggested, go to the single bolt adapter, then just order the correct hardware package from TT. That gives you the correct prop nuts with the 10-32 thread in the tip, and a press in 8mm bushing to properly center the backplate on the 8mm prop shaft.
Both ways will work fine. My personal choice would be to go the single bolt route, that way the stock spinner backplate can be used on other engines simply by changing the press in bushing to fit the prop bolt on any other engine with a standard prop shaft.
Regards to all,
Pete