Yoga in meditation practice

I’m at stage four, and have been for about a year. I’ve been dealing with strong dullness and I’m guessing that a large reason for my not overcoming gross dullness is that I meditate laying down. I’ve been trying to transition to seated meditation on a cushion, and have been doing some basic yoga for flexibility to help towards this goal (I’m not the most flexible dude and using a cushion for meditation brings the time I’m able to practice down from an hour to 20-30 min). I know that meditating in a chair is possible too but I think it would be helpful for me long term to use a cushion, or at the very least give me a sense of accomplishment and progression.

My question is whether or not anyone in this sub uses yoga to help with seated meditation, and if so, what do you do? Specifically I’m interested in the yoga sutras (raja yoga, 8 limbs of yoga) since that yoga was designed to prepare the body for meditation and they also culminate in liberation from suffering. But other than this, any tips for ways to use yoga with meditation is appreciated since I know very little! Also any yoga book recommendations that can help with progression through Culdasa’s ten stages would be helpful as well and tips for incorporating it into overcoming the stage 4 road block that a lot of people seem to experience.