My new cold frames...

The wife and finally cleaned up the side of the house (removed the brush, small trees &* stickers) late spring; Now we finally have a sunnier location that has a pumkin & watermellon patch and oh those zuchinis!! Anyway now that the summer is fading I planted another fall crop of radishes, carrots, spinach and lettuce on 8/1. Yes I am ambitious...I am reading two books by Eliot Coleman on the 4 season garden [Four Season Harvest: Organic vegatables from your home garden all year long] It prompted me to build 2 4X8 cold frames...I live in penn on the Delaware border I plan on planting the same mix in the cold frames on 9/1..

Anyone have any experience/suggestions with cold frames that they can share?? Am I too late for this season?? by all account spinach does really well..