If you plug the bypass in the housing you really should run no thermostat, or have plenty of holes drilled in it to allow adequate flow before the stat opens.

Something like 4 x 1/8” holes isn’t going to cut it.

3 or 4 x 3/8” holes would be more like it.

Obviously plugging the stock bypass hole isn’t something you do for cold weather operation...... it’s something you do to help control coolant temps in combos where it’s an issue.

Many of these builds will run at 170+ with no stat installed.

If I were running a combo with a plugged housing, I’d only run a stat if the motor just wouldn’t reach a somewhat normal operating temp without it.