if you actually intend to ride the bike a lot, the magic chain length really isnt a good long term solution. if you dont put many miles on the bike, and just ride it occasionally, then you're probably OK. as mentioned, too much chain tension will wear everythng quicker, and stretch the chain more quickly, which will lead to a problem since you have no tension adjustment anyway.

two solutions, which are readily available are an eccentric bottom bracket or rear hub, either of which are designed to allow for chain tension adjustment for vertical dropout frames.