I have about 250 hours with mine (high time 160hp O-320). It appears you are located in Vermont. If so and not operating from a very short airstrip, any pin setting will be fine to get started but I'd pick mid-range.
I'm based at 5,000' MSL. Most takeoffs/landings are performed at fairly high density altitude (7,000' and up), many above 10,000' DA. When operating from backcountry/short airstrips, I typically set the prop to the finest/climb pin/setting and takeoff/climb performance is very good, even at that high DA (though not fast at cruise). I used #7 for a couple months this summer and didn't care for it. As I recall, takeoff rpm (~7,000' DA) was around 2100. At full throttle cruise (10,000' DA) I could only get about 2600 rpm (all from memory). I suspect none of that matters to anyone as very few people routinely operate an RV-4 as I do. However; my real point that this prop offers some really nice flexibility/options if you need them - in addition to being a very nice prop (good performance, smooth, etc.).