Factory recommends 0.7-0.8mm, but I've found it as 0.5mm in SHERCOUSA booklet..any suggestion?

.6

Mr Turtle correctly quotes the NGK catalogue ?✌️ (Well, my 2016 edition anyway)..... 0.6 mm is the way to go 

The 0.5 recco was written long ago based upon the original Ducati ignition. The later Leonelli would do 0.7 just fine, and I suspect the current Hydria will be even better at it, thus the .7-.8 recco.

Take advantage of all you can get for better ignition.

 

iex plugs work better i think.

As it seems  0.7mm would be good to start with (as soon as I convince that Sherco clutch to let go). Thanks guys!