Ultra-Crispy Slow-Roasted Pork Shoulder but for a 20 lb full shoulder?

So I planned for Easter dinner tomorrow to do the slow roasted pork shoulder. I've never been able to get one with the skin on, but I had the opportunity and was excited to try.

One problem though, the family member who hooked us up with the pork shoulder drops it off and instead of an 8-12 lb shoulder it is a 20 lb shoulder.

The cut is definitely bigger than the one in the Ultra-Crispy Slow-Roasted Pork Shoulder. As far as I can tell it is the full shoulder, both "picnic shoulder" and "boston butt".

I'm hoping someone with a bit more knowledge can offer guidance as to whether I can still pull this off.

Should I try to cut it down? Or will it just need longer in the oven?

I was going to aim for 2pm dinner time with the full 2 hours of resting so I was going to start it in the middle of the night. Now I'm wondering if I need to start it even earlier.

Any help would be appreciated!