Now I have be careful and stay, I am being serious.... Which I am.

No, the high band antenna are not good for FM. Now because anything is an antenna to a degree, and say your high band was 30 ft outside compared to a dipole on the wall in the house, there is a good chance the high band will work better. But not because it's resonant or meant to work, but because it's outside and 30 ft up.

If you have am amp on it that has an FM trap on then no. And it's just about insane to not have the FM trap on if one is attempting to maximize high band reception.

And if you leave the FM trap off and the system has an amp, a few strong FMs will overload a lot of cheap to moderate receivers.

Since you don't need an amp with something like an FMSS or FM6. And most of the time 20 ft is good enough to be way up in the air, it's not expensive to install a separate FM antenna system.

If you are DXing on FM you really don't want an amp in most cases. Skip and tropo tend to be strong signals anyway.

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Conclusion will it work? Well if the station you need is just outside the range of your indoor antenna, most likely. If you need directionally or a lot of gain for a distance FM station, no.

Building that full size loop you found would work fine outside built out of copper pipe. If you could heliarc you could build one out of aluminum (a loop).

I have wondered if you built two of those loops would they still match a signal into the coax. Two of them in parallel would be about 37 ohms. But it would make it near omni if placed orthogonal to each other like an FMSS does with it's folded dipoles.

{WARNING JOKE} If you were a jeweler you could use titanium (joking again).{/WARNING JOKE}