This is a slow workout. We need it after the week we just had. If your shoulders are aching, give them a break. Just drop the SLRs. Won't hurt you a bit to do that.
I like to do this one in supersets. Remember back in the old days when you'd do a set of work and just sit there for a time while you recovered from it? After recovering you'd do another set of the same exercise. I can't stand to do that. Detest is a better word.
This GPP stuff has ruined me for the old ways. I GET that sometimes you have to revert back to the old ways. But as a true minimalist, I have a remarkable urge to economize my time - and yours.
Yes, we need to take 90 sec of rest between muscle groups so that they can recharge between sets. NEED it. The thing is, there would be nothing stopping us from resting those triceps while doing a set of DLs, right? The muscle groups of the DLs and triceps extensions aren't directly related. Going back and forth like that would even add to your cardio acumen. Cool. It's not really the purpose today, but it won't hurt.
It'd be different if, for example, you put triceps exts and pushups back to back. Triceps are a primary mover in the pushups exercise. They'd get no rest and going back and forth between those movements wouldn't serve our purposes today. That's not to say doing agonist supersets isn't a useful technique. It is. Just not today.
Fun to have these young men back with us again this year (Viewmont LAX). These gents are strong (body & character).