Thanks Stovepipe. You flatter me. Actually I am not at all sure that I know anything "perfectly well". In fact I feel very fallible, unlike so many here on this forum, judging by the tone they adopt
Personally, I have no intention of defending builder assistance programmes. They are very far from my own interests. As you rightly pointed out, they are anathema to the IAA (and SAAC too in my observation) and it seems unlikely that an aircraft built in this way would be accepted here. This is the key piece of information for Captain Slow, our original poster. It is clear that the FAA are also moving against these programmes so they may not be legal in the US for much longer.
You have a point regarding the plug-and-play panels. I had not considered those - also very far from my own interests. As regards firewall forward assemblies, they are definitely not available for RVs (can't really speak for other types), unless you consider the engine an 'assembly'. What Vans and others supply is a FWF kit http://www.vansaircraft.com/cgi-bin/catalog.cgi?ident=1241125563-174-204&browse=engines&product=FF_Kit
, with all the bits you need so that you don't forget anything and it can all be ordered together and will be compatible. The only labour the kit saves is cutting the hoses to the right length and putting on the end fittings. Vans also sell a wiring kit that comes close to being a loom but almost nobody gets away without having to alter it considerably. Unless you are on a builder assistance programme, by the time you have installed systems on a Vans plane you can't avoid having an intimate knowledge of every single small piece.
I am interested in the other items you mention though. Is it your opinion that 'real' builders must stitch their own upholstery and paint their own planes to be considered to be "in the spirit of the 51% rule"? Can you offer a rationale for what is acceptable to buy in and what is not? I assume you don't go so far as to say that no two pieces of material can be joined together other than by the builder, so where and how do you draw the line?
My core point is that even an RV builder who goes for every single time-saving option, is still going to spend way more time and carry out way more tasks than the combined efforts of the providers of those items. In fact, in every conceivable way, the builder of a completed RV has met the 51% rule and is entirely within the 'spirit' of the derrogation that we homebuilders enjoy. Furthermore, compared with the scratch/plans-builder, he has a far better chance of finishing out his project and getting some actual aviating done. Isn't that really the point at the end of the day?
I nearly forgot the pre-built tanks, In fact I got myself a pair of those - based on the opinions and the strong urging of my SAAC Inspector - maybe that's why they are so popular!