Rolf,
Im with you, if you can get to the jib and trim it to speed and to angle the boat feels more stable. Ive been on the back when going around the windward mark and no matter how much the main was "played", the boat wants to go staight down, bow first. I've always found that tight reaching the F18 the boat is responve(pretty dramatically) to the jib. The boat really doesnt like to tight reach without the spin, so somebody better have that jibsheet in their hand!
Jake and I pitched around "A" at the NA"s in the last race, I think because I couldnt get the jib out early enough, he thinks because I went up front to grab it, but whatever, the combination of those 2 things turned us upside down quickly, even while blowing the main. It was blowing 20+ so who knows...