The Platt Spit does not have, nor does it need, any changes to the outlines or airfoils. It looks the part and flies like a big trainer. Platt's plans are quite old but still good and the airplane appears to be fairly simple to build by Spitfire standards. (I owned and flew one but did not build it, only rebuilt it!) Platt does not include much in the way of instructions so you will definitely be on your own there. Platt's glass accessories are generally useable but not really up to modern standards. Same for his retract units. They will work in the Spit but not without some mods to the retract angles. I'd go with the Yellow retracts were it me. If you want a true 1/5 size Spitfire that is built up, flies good, and is accurate then the Platt is about the only game in town.

PS - The G-38 would surely fly it fine but I don't know how it would fit in the nose.