I'm trying to use some of the FS4 scenery files that are hosted on this site, but I am getting the following error: "File too large for current memory allocation"

I'm running in Dosbox 0.74. The config file has "memsize=16". I've tried changing that, but no luck. XMS and EMS are both marked as true. Is there a setting in FS4 that I need to change? Something in the "Aircraft & Scenery Designer" program I need to change?