Training Maxes for Supplemental Lifts?

I am considering using some of the alternate lifts for supplemental work as defined in 531 Forever. When reading that section of the book I was under the impression that you should establish a training max for a lift, then use those percentages for the FSL or SSL.

For example, say I wanted to do floor press for 5x5 @ FSL as my bench press supplemental work. Should I establish a training max for floor press and then use those percentages for FSL?

Also, after establishing said training max and using it in the manner stated above, would I also do a TM Test on 7th Week Protocol for floor press and increase the TM along with my bench press? Or should you only increase the TM on the main lifts for that round of training?

Finally, does anyone have a rough process they use for establishing a TM for a lift they haven’t done much? I imagine I would just estimate a 1 rep max according to what I have done it for in the past and then work up to 90% of the projected max for a PR set.

Any input is greatly appreciated.

I just do all my supplemental work at the prescribed percentages of the main lift. If your TM is set correctly then this isn’t a big deal in most programs

I’ve worked up supplemental lifts when starting them to get a rough idea TM. I’ve done this only when doing FSL.
I usually start with the bar and add weight as I estimate what I can do. Stop at a challenging but doable 5 reps. I use Jim’s TM calculator. Take about 85% and go. I haven’t done 7 th week for supplemental but add 5/10 lb for upper/ lower.
If I have a decent idea for the lift of my max , I just take the % I need for the program.

I’ve done this when using floor press for BP
CG for BP
Behind the neck for press ( I really like this exercise).
I just squat more for squats
Good morning for DL. I worked to a decent 8 rep, then figured my max , and took 50 for my TM and did BBB.

The reason you are under this impression is because I say it pretty bluntly, “You must find the TM for the supplemental lift.”

So let’s say you have to do floor presses. The first day you try them, you work up to a 5RM and then use that as your TM. So now you have your TM. On that same day, you do the correct sets/reps for the supplemental work. Unless your bench press is over 600lbs, I can’t imagine working up to a 5RM takes that much time as you have a GENERAL idea of what you are lifting (based on your bench press). Just use some common sense and make reasonable jumps. Maybe I’m missing something? it’s pretty easy to do; you can use the rep max calculator also in determining the estimated 1RM and go from there.

Thankyou, I appreciate the input.