Adding Insulation to floored attic
While updating some electrical, I recently removed the flooring in my 1936 2-story attic to find 2x6 joist and roughly 4" of loose wool insulation. I need to add more insulation, but still be able to put some plywood down and use the attic for storage. I live in the Midwest and the recommended R value for attics in my area is R-38. With only 5.5" of space to work with, I don't know if I can get over an R-19 (maybe 21). I have considered a couple options and I would appreciate any feedback or suggestions that would be the best bang for my buck.
1. Add more blown-in insulation to the floor joist under the plywood flooring. Also add batt insulation to the rafters of the roof for added insulation. Probably the cheapest option, but don't know if it would do any good.
2. Raise the attic floor to accommodate more insulation. I don't really want to do this being it will be difficult and expensive.
3. Remove existing insulation and have professionals spray in expanding foam into the joist. I was told by a pro that I would get around a R-35 with only 5.5" of space. I'm not leaning this way because of the huge price tag that goes w/ expanding spray.
Any suggestions or other options would be very helpful.