You may want to look into smaller new world chiclids like firemouths, convicts, cutteri, or honduran red points. One of these guys would work fine with the synos...
FWIW, my L204s (Flash Plecos) are anything but sedentary. They are very active and fast little buggers, and rather pushy with each other (though fortunately they're ignoring the otos & endlers I have them in with). That said, I know less than nothing about puffers.