If you have a flight test program, and that includes recording data, then the second person is a crew member for the purposes of tracking data
I informally ran it past the FSDO here a few months back and they said it was plausible if one were working on an entirely new design or a significantly new design. I happen to be doing so which is why I had inquired about it. The guy I spoke with said it would have to be included in the operating limitations or that I could simply ask for the operating instructions to stipulate two pilots are required (which is how I plan to fly it anyhow, especially when doing IFR operations in actual IMC) and then amend them after the fact if I want to remove the restriction.

If you're just afraid to or uncomfortable with flying your new RV-6, you'll have a much tougher time most likely.