Having just gone through building my own harness for the G3X system, I have to say that it?s much easier and fun than I thought it would be. I was just like you in thinking that it was a major headache and not something I wanted to mess with but decided to do it for educational purposes and I?m sure glad I did.
One thing I did was get a little help with an interconnect diagram. That took a lot of the puzzling out of it. Whichever dealer you choose likely has that as an option. I used Stark Avionics and have been very happy with his support through the process. The other thing I did was attend the AEA experimental avionics course. The course was well worth the time and money but I wouldn?t consider it mandatory. If you have someone available to show you the basics of building the Can Bus and assembling the connectors you should be good to go.
I realize this doesn?t really answer your question about shops that build good wire harnesses. A friend encouraged me to build my own when I planning to farm out the work and I?m definitely glad he did.
Fixing the panel to be the way you like it is easy! I agree with you on the lack of standardization. I have not been able to find any research on panel layout with an EFIS, particularly things like where to put radios, toggle switch groupings, etc. Also, when you throw a tablet into the mix, it becomes even more complex. It would be interesting to hear your views on the perfect panel.This is an interesting thread, can learn a lot about this stuff Had a look at Stein's website, impressive.
The one thing I notice with Vans A/C & no doubt a lot of other kit builder designs is that the panels are all over the place. I've been looking for an 8 for ages now inc 7's & the one thing that puts me off most of them is the panel! It's like some stand back throw a dart & where it lands is where the next instrument goes. A couple I've looked at have functional panels but have issues elsewhere. I guess for me coming from a commercial flying background one gets used to standardization, something that doesn't exist in the experimental world. Still it's interesting to see what's inside the heads of Vans owners