| I would definitely go smaller. I wouldn't even use my Mag7 to empty into a 5 gallon bucket. I use a Maxijet1200 with 3/8" tubing and fill a 5 gallon bucket in about a minute. A little faster would be nice but it doesn't come shooting out with some tremendous force and I have plenty of time to stop it before overfilling.
How big is your mixing container? I had a mag 7 in a 30 gallon trashcan and that was plenty of current to mix.
Though I did once use my mag 7 to originally fill my tank from the trashcan. And going up 5.5' through 3/8" tubing, it didn't have too much force. But the tube was also loosely held in to the pump outlet so there was some loss of pressure there and it still emptied the can relatively quickly. | 
