i get the same problem. last gig i was in a bar with my master on 1 and i was shaking the entire bar. the sound guy there was shit, but i was way overpowering

I will tell you how I manage, but I have to warn you, sometimes when I read what some people post on this forum I wonder if I am playing through the same amp as they are.  And don't get me wrong, these folks seem to know a lot more about amps than I do. Maybe I am not picky enough, but have not really had a bad experience with the OTS.

I play mainly in clubs that have a dance floor around 15' x 25', about ten tables (seat 50 -60) and a bar in the back. When we sound check, we set the volume so people can converse at the bar (with a raised voice, kind of shouting). I mic my amp through the mixer. I put baffles in a "v" shape in front of the speakers, mainly so I can hear the mix in the monitor (over the amp output ) and to attenuate the level somewhat. Here is the controversy: I use a TC G-sharp , in the loop with a BBE 482i and if I stay at or above 12 O'Clock on the G Sharp's level,  I don't lose any noticeable tone, but I can lower the volume somewhat . Others on this forum seem to be dissatisfied with this set-up,  but it sounds good to me and other people listening seem to think so.   I also use a couple Tube Screamer style pedals in series (usually a fulldrive 2, with an OD 9 or RT66, it really doesn't seem to matter all that much) and I can cut the volume to a point with out losing tone with the volume control on the OD pedals(and I can bring it up in a hurry by adding an OD pedal). 

We play a pretty broad mix of music and I change my guitar tone significantly,  2 or 3 times, at least, in a 10 song set. I also switch from an LP to a Strat for some sets. I use all the settings on the the OTS to get the right tone for the song being played and it would take way too much time to explain it all  but the switch settings affect volume greatly as well. It has taken me several gigs to get the settings right and I am still perfecting things. I have attached a picture of my rig, its not too great, but you get the idea. Ignore the blue box on top of the amp, that was another experiment.

One will definetely be better off with a 2x12 if volume is a problem.

JohnE  - What kind of material do you use for the baffle ? Do you stille hear the amp on stage or do you have your guitar in the monitors ?

I REALLY don't like my guitar in the monitors...... Gets too spikey and strange   

Make the singer go out and buy himself an In Ear system !!!! :-) 

HA !!!!! Good one ! :-)

Yeah - thought about that but I really don't like the sound of my guitar in a monitor....really ruins my mood to play.... maybe I should just accept it and start looking for an In Ear system as well  and then put the speaker in a closed flight and mike it in there....

I'm not familiar with the Kleinulator, I use another type of Dumblelator clone and it has a "return" pot that I use to essentially set the whole volume of the rig.  I use it as the overall master.  I got this idea from reading another forum.  It isn't perfect but it does help.  I'm sure the Kleinulator works the same way.  Set your amp up volume wise where you need to be then start backing down the return.  Then start playing around with the interaction between the tone you're achieving and the master volume on the OTS until you strike a happy medium.

If I had another $500 lying around I'd plunk down for an Ultimate Attenuator.  There is no club or private event that I play that I could ever let the OTS sing above 5 on the master.  I think this is also where the amp just starts to really shine.  For this reason alone, the OTS may not be the amp for me, but I got to tell you it does have some kewl mojo and I think its a spectacular amp for the money.

I hate having alot of guitar in the monitors too fwtw.

jim