I own several small wheel bike Fridays. Tires will do more for you than any other component. I inflate my 40mm 406 tires to ~50-55psi depending on cargo. 70psi in a 50mm tire sounds like way too much pressure unless you are carrying a lot of weight. If you can get a helper sit on the bike static with whatever cargo/gear you typically ride with measure the change in tire deflection before and after getting on with your gear. Adjust your pressure until you get ~15% of the tire's 50mm width = 7-8mm in vertical drop. That pressure should give you a good blend of comfort and performance. Note the pressure you end up with in each tire and if you are satisfied with it just inflate to that pressure next time without measuring anything.