This is a system I learned many moons ago when I hooked up with some enterprising types in grad school. It is fun, action-oriented, probably more suited to MP than IMP. I play it occasionally at BBO with a pard who helped develop it. The gist of the system: No 5 card suit? no problem, just open your highest ranking 4-card suit at the 2 level (except of course, 2♣, which is strong and artificial). Ergo, almost always when you open 1 of a suit, you will have 5 of them. We open hands with 10-15HCP. We overcall with 10-15HCP. If you are a passed hand, that means you do not have 10pts. Takeout dbl= 16+ If pard opens 2♦/♥/♠, single raise = forcing, new suit = "pass me pard", 2nt = show me other 4-card suit (or bid 3♣ if no other) 1NT = 16-18, may be unbalanced (even with a void!); if your pard tries to transfer to a suit where you have a singleton or void, you just refuse the transfer. Preempts = 10-15HCP with 6 or 7 length Reverses do NOT show extras. Hmm, that is the Cliff's notes version. :)