With the small opening where the line comes out on a spincast reel, I don't think it will even touch the first guide of a spinning rod. I'm not saying that using a spincast reel on a spinning rod is preferable, just that it is possible. Theoretically a spinning and a casting rod would have the eye's mounted opposite of each other in regards to the spine of the blank. On a mass produced rod I don't know how much attention is even paid to how the spine runs. I would expect that to be taken into consideration on a higher quality rod.

I have them mounted on rods from walmart that are over 10 years old, that are mainly guest/ grandchildren rods.