If I may add a little to the discussion...
I originally bought the RISR because I wasn't happy with the Magpul cheek riser solution ( have to extend the stock to charge the weapon ). I was looking for a cheek riser that would work with a collapsible stock, after literally burning my cheek after shooting one hot summer day. Might have been the weather and not the stock itself, but after using the RISR, never had that burning sensation again...
The RISR did put my LOS a little higher than my irons AND an older EOTech sight I picked up elsewhere. Without the RISR, the EO and my irons were perfectly co-witnessed.
I bought the LT 110, to raise the EOTech, which it did, and with the LT-110 / RISR combination, I had perfect LOS with my EO, and lower 1/3rd co-witness for my irons. I later added a magnifier and the LT-602 Short.
When I drop the LT-110 / LT-602 / magnifier / EO, it IS a little uncomfortable scrunching down to use the irons, but I don't have a problem putting lead on target consistently enough to not worry about it much...