If you think you could make your own antenna, then why not? Being a cheap, I'd much rather make something than buy it if I can.
Having said that, a vertical antenna just isn't ever going to be my first choice. I live in a very noisy place (man made noise), hate messing with radials, and have found that the horizontal antennas are just as 'good' as a vertical in most cases. I don't have to worry about restrictions and as long as an antenna works well I'm not too concerned on what it may look like.
But, if I wanted a vertical antenna for more than one or two bands then I'd certainly give it a shot. Most commercial antenna manufacturers think more of their products than I do (cheap, remember?), and if they can make one I figure I can at least get 'close'.
Have fun.
- 'Doc