for my first built b18c (pistons/rods) i changed the oil at 100 miles, 500, 1000, then 1500 with regular 5w-30 oil. then you can change again at 3k miles with synthetic and keep using it from then on. i wouldn't go 6k miles between oil changes on a boosted motor...stick with 3-4k between changes to be safe.
and i think 5w-20 is too light...if you rebuilt the motor with oem parts i'd say stick to what honda recommends, 5w-30 or 10w-30. for built motors some ppl like to go thicker. i've tried a bunch of weights and personally like 5w-40 (i use it in my 1.8t audi and in the teg during the winter) and 5w-50 the best.