A bad idea? Not particularly. As already said (sort of), if you have a particular need for a horizontally polarized antenna, or maybe a 'sort of' directional antenna, then why not? There are alternatives though, as already stated. Once you get past the directional thingy, and the polarization thingy, there's no particular benefit from a dipole on 2 meters or 70 Cm. Then again, if you just want to, then why not?
- 'Doc