I bet your clutch steels are warped, the thumper is slipperyer, clutch warps quicker from slipping but the warped plates respond better to the slippy oil.
you could try some moreys at 10% with the delo, that will get a bit longer out of your warped plates, if you'd used delo from the start the chutch would still be fine. thats what Ive found at least.
2 guys I know have been using delo for a year in their rice burners, they both changed oil together on the weekend and used up the last of some belray thumper..... both clutches went about 1 hr later.
the difference between the 2 is nothing to be worried about, its just that the thumper is slippereyer if thats a word.