I don't do the doorway versions of the pec minor stretches. I do the floor based ones:

"Lie flat": Lie on your back with legs bent, one arm overhead. Anchor the hand of that arm with something like a book or weighted ball. Let legs drop away from that arm. Feel the stretch. Reference: 9.1 Chest Pectoralis Major & Minor Stretch - YouTube

"Half foam roller": Once the above is comfortable, lie on a half foam roller and do the same stretch though you won't likely need the weight on your hand. You can also stretch out to the side for a chest stretch. I use the half roller "OPTP PRO-Roller Soft Density Foam Roller" at Robot Check

"Full foam roller": Once the above is comfortable, you could possible go to a full foam roller.

"Swiss ball": Once the above is comfortable, you could use a swiss ball.

I'm still on the half foam roller after my pec minor syndrome flared up on me after neglecting to stretch it for months.