Hi Andrew. That's what I like about this forum - fast replies. Thanks.
I tried the prop nuts for the for the Syma x8 and they worked, as u probably u can use the phantom props on the Syma. But, I found an old phantom prop and tried it and as u said it wouldn't tighten up.From further inspect I found that the reason was not the threads but the shaft on the solo is not long enough to read the Solo Shaft screw. I guess with a little mod to the phantom prop they would work, but I wouldn't try it since Solo props are now available just as cheap as the Phantom.
Bill