I went from 306 to 407 on my 55 and happy I did so. You also don’t need to install a valve.
Here’s from their manual
“ Once the filter is operating continuously, you can use the top lever on the AquaStop to regulate the water flow.
To reduce the water flow, lift the lever up to halfway, but no higher. This can be done once the unit is fully operational, and will not harm the motor. However, never run the filter with the lever up (closed) more than half way.”