Define "slightly" too big. A switch to 700c wheels will lower the bike by a little less than 1/4 inch. Not a lot for sure, but it would not have all of the negative factors above either. Kind of expensive change to get 1/4 inch, but if you have some wheels handy, you could try it and see if it makes a difference. With that change, you will need an additional 4mm of brake caliper reach. Many calipers, but not all, can do it.