Finger joint.... I'm seeing one thing, but something tells me your seeing something else. You talking about small 1" wide flooring? Or just boards milled with a tongue & groove for flooring????

Why would finger-joint prevent staining? Finger-joint is a way of joining the stile and rail or casing of a typical window and when done well, is a very strong joint. They should be invisible when one looks at the stile and the rail. Even if they are visible, as in some older well made high quality furniture, owners normally stain them to show off the fine construction. We had two all wood windows before replacing them with AL clad. We stained the exterior wood with multiple coats of marine-grade stain once a year. They held up really well for over 9 years in searing 100 degree heat and wet and cold. If we did not become tired of the annual cleaning and staining, we would have kept them.

My ring fingers are longer. no arthritis yet but... Rheumatoid Arthritis runs VERY strong in my family and according to my PCP I have an unusually high probability of developing it because I have auto-immune anemia. Now, you know I will be checking my family's fingers next time I am in Atlanta. Comparing the half of my dad's family with arthritis with my mom's half that doesn't! LOL

" Does anyone have any experience with this?" No I don't. I've never heard of flooring in 20 foot leingths,much less tried installing it. What is it about 20 foot finger jointed boards that appeal's to you?