So, I can make a modeline that works in 15KHz for the Radeon 6670 in linux.  But when I tried running switchres with the --xrandr option for puckman, this is what I get:
Error with command line args
seth@Neo-Arcade:~$ switchres puckman --xrandr
[] "puckman" vertical 288x224@60.606 (1.286) --> 400x288@60.606 (1.389)
X Error of failed request:  BadValue (integer parameter out of range for operation)
  Major opcode of failed request:  129 (XFree86-VidModeExtension)
  Minor opcode of failed request:  10 (XF86VidModeSwitchToMode)
  Value in failed request:  0x14f
  Serial number of failed request:  135
  Current serial number in output stream:  137
seth@Neo-Arcade:~$ switchres puckman --xrandr --mo 0
[] "puckman" vertical 288x224@60.606 (1.286) --> 400x288@60.606 (1.389)
X Error of failed request:  BadValue (integer parameter out of range for operation)
  Major opcode of failed request:  129 (XFree86-VidModeExtension)
  Minor opcode of failed request:  10 (XF86VidModeSwitchToMode)
  Value in failed request:  0x14f
  Serial number of failed request:  135
  Current serial number in output stream:  137
I have to be doing something wrong.  It's pretty essential to get this working, so I can run games like Kobo Deluxe, Rom Check Fail (which has an odd alsa/pulse issue), smc, and a few others.  Calamity, ves, thoughts on what I'm doing wrong both in Ubuntu and Groovy Arcade?