I bought a partial finish kit for my RV-3B some time ago, when I was finishing the wings, I think. My philosophy was that I wanted to keep one kit ahead of what was next so that I'd have no delays. I had an engine already, so many of those decisions were defined and for the RV-3B, there's no FWF kit anyway. But I had Van's include such items as I could identify in with the finish kit.
The kit is still sitting there, taking up room in my hangar. I seem to be going very slowly. Couldn't have gotten this kit without sufficient storage.
Since I ordered my kit, I noted that Van's has improved certain things, notably the cowl material. That possibility of continuing product improvement, while limited on my model, might affect an RV-8 more.
Once I had figured out some of my systems to-be, I was able to keep an eye out for the occasional deal, acquiring some of those components. That's been good for me, as I was able to incorporate some of the mounting arrangements into the basic fuselage construction on a timely basis. This also might perhaps be more an RV-3B thing than an RV-8 thing, but I must say that it certainly made some things a bunch easier. The transponder, for example, attaches to the longerons behind the baggage compartment, and it would have been tough to mount it later.