In simple terms - you can plug ***any*** electrical instrument into ***any*** amp.  Bass, mandolin, mic keyboard, banjo, etc, etc...  In the 50's & 60's it was common to plug a mic into a guitar amp for vocals.  An amplifier takes a small electrical signal (any signal) and makes it larger.

As explained in great detail by Roly, the problem lies with the speakers.  The speakers provided in guitar combo amps are not designed for bass.

If you like the sound of a guitar amp, get a properly matched (impedance - if you don't know what that is, look it up - you need to know it) bass speaker and rock on.

I regularly use a '79 Traynor Monoblock II amp with a Hartke 410 cab for bass or a Fender 112 cab for guitar.  I have also used my '72 Fender Princeton Reverb for bass at low volumes.

Hey, I know it's 6 months late, but the answer to your question is yes.  I just installed a set on mine.  Use the 16" Twin size.  Unscrew the 2 side chassis screws and remove the washers.  Use the longer screws that come with the legs and attach the legs in the existing holes.  (Yes, I dropped my chassis down and there is a nut formed in the chassis for the screws to tighten into, so you can save the time of doing that).  Set your legs on an angle you like and screw in the washer guides in place.  Job done - enjoy!

BTW, I was a dedicated tube man unitl I tried the Frontman 212R a year ago.  I've only turned my '72 Princeton Reverb on 3 times since then.  The frontman is an incredible amp!!!