in my recent game i've started a major war on first Natives, then England and at last Greek and got the idea to capture their towns till they was ready for vassalizion and release the towns i'd captured into a colony ... is this a dueable tactic or do you lose more from smaller vassals than good is? (got French, Vikings, Egypt and America as colonies and England and greek as Vassals)

IMO, if you're going to release the captured cities as colonies anyway, you may want to instead liberate the captured cities back to their original owners for the positive diplo points.

As the previous poster (with the unspeakable nick :p) said... Releasing cities back to the Capitulated Vassal is often better than making those colonies...

Just watch out - not to give back too many cities, so the Vassal does not go over the "Get Free" threshold.