Here are three of my chastity devices. One standart, one nub and one where I cut the front off.
The nub pinches my skin, so its a no go.
The cut one is really good for long term due to ease of cleaning, but I managed to cum with it on, since I have access to the tip of my dick.
In the end Im now wearing a larger metal one. Its a bit heavy but seems to be doing fine.