I'm installing 3/4 oak hardwood floors in a long room (45') and the floor is flat, with one exception. The house is a 100+ year old brick townhome with the back half built at a later date. Midway through the room (where the "extension" starts) the plane of the subfloor changes such that a slight crown is created running perpendicular to the direction of the intended hardwood install. There are no signs of recent settlement in the house.
While the angle is relatively slight, due to its position in the middle of the floor, I'm wondering what the best way to approach this is. My current thought is to sand the crown to take the edge off and lay a row of shingles on each side to make the change more gradual. I'm leaning in this direction because previously there were hardwood floors laid in the room and I never noticed a crown in the floor. I thought about adding sleepers, but I worry that fixing the angle over 20+ feet would make the sleepers way too large at the far wall. Does my approach seem reasonable?