Most, if not all, IMP plans were drawn by Claude Baskin. I have a set of his P-51A / A-36 plans which I purchased from IMP. The plans look decent enough but are pretty sparse, ie, no rectracts, radio, engine installations shown. All this is left up to the builder to decide. I don't know if the Spit plans are the same but it's not necessarily an issue if you have the experience. My .02 cents worth.