6'2" been there, got the T-shirt. The RM is such a good base to start from (unlike the YZ), the 2 best mods on my bike (out of 100's$$$) was to lower the footpeg, you can cut the spacer of the peg mount and weld it to the top, this drops the peg 1/2 an inch. you can also get the applied bar mount with the Windam protaper bend or the Carmicheal renthal fatbars, the whole setup is less than $200 from motosportoutlet for everything. the ktm bend are even more straight but not as high.
if all that doesnt work, do to you local dealer and sit on an 03 KX and just thank your lucky stars you didnt buy one of them because they feel even smaller than the yz's!:)