...or you might try a different way of holding the guitar while sitting.

Try a modified classical position, i.e., one with the guitar in front instead of to the side. Kinda cradled between the legs, not off to the side on one thigh. This could have an added benefit of having the guitar in same position (in front) while sitting as while standing. That's generally considered to make the transition of playing from sitting to standing easier. Further, I've read that such positioning helps with stretch...affords a longer stretch/easier reach.

I changed to this way of holding a guitar when my dreadnaught proved too large to comfortably hold/play in the 'regular' way while sitting. I always play sitting and I always play with this modified classical position.

What's important is to hold and play in a way that is comfortable for you and with the guitar positioned in a way that helps, not hinders, the fret hand with reach, stretch, etc.