Hey all. Long time lurker, first time poster.
Last week, I received my new RF 87U 55g from EK. Before pulling the trigger, I had a really hard time deciding between the 45g and 55g. I was worried that the 45g would be too light and/or that the 55g would be too stiff. I've used all of the 45g Cherry MX switches and found them to be too light, but since Topre has a different force curve than Cherry MX, I thought that 45g might feel different on Topre. In any case, I'm extremely happy with the 55g switches. They feel just a little stiffer than a Cherry MX Blue or Brown, and about as stiff as a lot of other rubber dome boards (e.g., the Dell SK-8115 provided by my work, which the RF replaced).
So, for anyone considering going with a 55g uniform Topre board, this seems like a reasonable rule of thumb: if a Cherry MX Blue or Brown is too light for you, and most common rubber dome boards feel about right in terms of stiffness, a RF 55g probably won't be too stiff for you.