DanSolo: I'm playing this with the eRampage mod. It's rendered in openGL and looks way better. Plus it increases the speed of the game so it's more playable.
I play Duke, RR, and Blood using DOSBOX and 800x600 in the setup.exe.
If you edit your DOSBOX conf file I do it like this for the best look and smooth speed:
[sdl]
fullscreen=true
fulldouble=true
fullresolution=1280x720
windowresolution=800x600
output=ddraw
Of course you can make the fullscreen be 1920x1080 if you prefer, but keep the window res at 800x600 (what the game will be emulated at, matching the setup.exe setting).
Now I am not sure why DOSBOX doesnt begin with output=ddraw from the start, because I had nothing but problems with the default setting it was on. It makes the game's window mode not fill the screen up. But with ddraw output, the 800x600 game resolution is stretched to fill the screen in fullscreen mode. So I am playing on 720p with the game running at 800x600 but actually filling my screen at about 900x720 and keeping the correct 4:3 aspect ratio. This works perfectly with Blood and Duke3D as well.
And one last setting if the game is emulating slow...
[cpu]
core=auto
cycles=max
This just makes sure DOSBOX is using your CPU to the very maximum it can, aka higher framerates and smoother gameplay. I can run all the build games smooth on my 3.0 ghz Core 2 Duo, except a few levels in Blood where they use snow or other atmospheric effects, the game for some reason lags badly then in DOSBOX. That is a known issue however and will lag any CPU with DOSBOX. even very current ones. I dont think Redneck Rampage even uses such heavy sprite effects in any of its levels so no worries.