Is HOPO-cidal Maniac  only achievable with Guitar or will Bass do? I don't play Guitar so if it's only achievable with Guitar, I'm Shit out of Luck.

I don't see why Bass wouldn't work, however... if you can play bass, why don't you play guitar?

No help on the achievement here, but I also prefer Bass.  In my mind (and there is no real reason for this) I find playing plastic instrument Bass to be somehow more reasonable than plastic instrument guitar.  I have no idea why, I just get more into it.  And I like upstruming too. 

Always Be Up-strumming

" Always Be Up-strumming "

" @ShaggyChu said:

" Always Be Up-strumming "

Never not up-strumming. "

One of the Career Goals is to hit 1000 HO-PO's on bass.
 
May I recommend the song "No Regrets" ;)

Wait, what? People who aren't this one douchey friend I had in high school only upstrum, even on guitar? I had no idea.

I think the HOPOcidal maniac goal is listed under "Epic Guitar Goals", so it might be for guitar parts only.  Don't know for certain.
 
Also: Bass = upstrumming.  The bass in my house gets played on the Hoffner or Madcatz P-Bass, and upstrumming, IMO, just makes it feel like a different exercise than playing guitar.

A little side note on HOPOcidal Maniac (and all related goals): Tapping during the solos DOES COUNT TOWARDS THE GOAL. If you tap a note and then tap a HOPO after it without breaking streak, it will count as a HOPO instead of a tap. Those of you that exported Rock Band 1, get used to grinding Green Grass And High Tides if you want the goal fast. Alternatively, wait for the Harmonix Free DLC (the tracks from RB2 by Harmonix bands) to hit and grind Visions if you can consistently FC it.

" A little side note on HOPOcidal Maniac (and all related goals): Tapping during the solos DOES COUNT TOWARDS THE GOAL. If you tap a note and then tap a HOPO after it without breaking streak, it will count as a HOPO instead of a tap. Those of you that exported Rock Band 1, get used to grinding Green Grass And High Tides if you want the goal fast. Alternatively, wait for the Harmonix Free DLC (the tracks from RB2 by Harmonix bands) to hit and grind Visions if you can consistently FC it. "

So... the last time I checked, I had hit around 40,000 HOPO's.
 
I don't know what I'm gonna do once I get this achievement :(

" @TheGreatGuero: I find Bass more fun, I upstrum only so it makes Bass fun. I mean if push came to shove I could play Guitar but I prefer Bass.  On a little side note, has anyone played Jerry was a Racecar Driver on Bass, Holy Shit. "

It is ONLY achievable by playing guitar. Kind of silly, but that's the case.