Series 1, 2, 3 to GP

Hello everybody, I am seeking feedback from anyone with knowledge and experience in building, repairing, and/or living with any of the twin cylinder setups i.e. Targa Twin, Chimera, et al. I have always loved the concept since reading about the Innocenti prototype decades ago, and the thought of creating something similar sounds appealing. Yes, I am well aware there are simpler and cheaper ways to go about things, but thats not the point. I am looking for input regarding conversion-related problems as well as support (or lack thereof) from the kit makers. FWIW the end goal is not high hp but more about creating something in the style of what Innocenti might have produced; conservative port timing, piston controlled cylinders, 2-into1 stock-looking expansion box, full panels. Thank you!