That's fine man I appreciate the honesty. He's in a 20 gallon right now, a tank that I typically use for QT. He's been in it for about 3 weeks now and seems to be doing ok. This whole biocube thing is going be on sort of a trial basis as I will make other plans if things start to go south for the puffer.
That being said I disagree with your take on tobies being aggressive fish. The only thing I have ever heard about tobies is that they will sometimes nip the fins of other fish (mine did this once and the behavior never reoccurred). Even their defenses are passive, with their toxic mucous coating and their ability to "puff" up as a means to deter predators. With this fish in particular, I've never seen him become aggressive with any other fish, including some that were smaller than him. That combined with the fact that he is not an active swimmer leads me to believe that he has a good chance of living well in the smaller tank.
Now could that change in this different environment? It's possible but I won't know until I try it.
I also tend to take clowntriggerfs' hands on opinion as being a good indicator of the possibility of success with my puffers introduction into the cube. He's given me a lot of good advice in the past (I'm not saying you're not giving good advice or that he's more knowledgeable than you, just that his advice hasn't yet steered me wrong).
Please don't take this as being combative as that's not where I'm coming from at all. I'm just offering some counter points. Just a friendly debate!
The wrasse I'm really leaning away from as no one has given them a shining recommendation as a good addition to a cube but that's why I'm asking. To make sure if the idea is good or bad. The flasher wrasse is definitely out but it doesn't hurt to explore other possibilities, especially as I was recommended the pinstripe by another aquarist.
If not a wrasse it'll probably be a Royal Gramma as I'm pretty sure I've seen people keep those successfully in nano tank.