Suburi in Bogu is actually very very hard even for the experienced. It is because we have kote and men on. Then we need to stop our shinai in the air. With kote, that is harder. Plus, we have men-dare (flappy parts of men), which makes lifting shinai very hard.
The better time to do suburi in bogu is actually at the end of training. Needless to say, it is very hard 🙂