$$$$$. I don't know how well those kickers work, but I don't think of 27'ers as having rigid vangs.
Why not? The Cat 27 we looked at, all tricked-out for racing, had one. Yeah, they're expensive.
Some comments I saw on this subject on Brion Toss' forum indicated that for other than racers, a boom kicker plus topping lift is better than a rigid boom vang, however.
Why the topping lift if you've got the boom kicker? In heavy air and seas you're going to need to hold onto that boom for dear life when reefing or taking the main down. The kicker isn't going to hold that boom up steadily with your weight bouncing up and down on it.