I just test flew on Sunday the V-Mar RV-4 with flaps and an OS46fx. The 46 is more than enough power for this aircraft.
Be careful with the flaps, make sure you use enough throttle to compensate for the flaps, they are very effective. AS for the construction, I too was reluctant to purchase one of these ARF's because of the bad puiblicity. After looking it over I think that they have come along way in a short time. There are a few weak places, but the only place that was of concern to me was before and after the main landing gear, a bit flimsy, but the main gear blocks are solid. This plane flies very well and at lower speeds,
(not slower) it did not appear to have any bad habits. I like it and I am glad that I purchased it.

Ted Zaborski