a standard xr3i will be higher than a standard rst if its the same as fiestas. as the xr2i is 20mm higher than a fiesta rst, so wont be any different if you get 40mm rst ones or 60mm xr ones.

good luck with the hunt, if all fails, grinder and zip ties are your friends

edited to say: love the colour of your rs, is it a dark metalic blue?