My real beef with Lisa/Skupin right now is that, at 4 people left, there will be a 2-2 split and it comes down to some random task (fire-building, or "the stones") instead of voting strategy. They should have anticipated that and gone for Denise when there were six people left.
In general, a 4-person alliance with 2 teams of 2 is a bad idea. Penner should've joined the proposed alliance then secretly brought on board a 5th, who would've been a 3rd with him and Carter.