In Win2K or WinXP you can right-click on the DOS window's menu bar, select Properties, then Fonts. If you switch to Lucida Console even larger fonts are selectable. Have you tried using Lucida rather than Raster fonts? See my comments in Thread182-627060 and Thread779-623690. (Yes, I pasted this from another thread and just found out that someone deleted that thread 627060.)
Have you tried running it within Command.com rather than Cmd.exe? Having a DOS window (or several) open can cause Windows to slow down too, depending on the application. Has something to do with how the DOS programs keep polling the keyboard or whatever. Using Command.com and moving the sensitivity property to the right can alleviate that issue.
dbMark