You can surely INSTALL the highest possible resolution texture for CYVR, so you won't have to go through the installation again (it's fairly long, since all textures must be regenerated on the fly), but set the maximum size in the Addon Manager to be 2048 or 1024 to save RAM.
Even if textures are in 4096 size, if the setting in the Addon Manager (which controls the FSX.CFG anyway) is set to a lower value, that will be the value used, you'll just waste a bit more of hard drive space to store HD texture you won't see.
Another thing you can try, is to *install* CYVR with building textures at 4096 or 2048, and Shadows textures at 1024, and keep them at 2048 or 4096 in the sim, so you'll save some memory without compromise too much with sharpness. A bit of blurring in shadows is way less noticeable if the rest of the scenery is sharp.
