Confused with relationship btw FSP and WOD

Apologies in advance if this has been posted elsewhere, I just can't find it.

Background: have BtGB book and followed killroy's beginner plan for 1 year. Have just started doing WODs.

I warm up with FSP training. If I can hold BL flat tuck 40s, FL tuck 40s, adv FS 25s, Lsit low 20s, should my FSP warmup be with those positions (at 50% time intervals) or easier variations (at 50% of my max hold for those)?

Then when I complete the WOD, if the program calls for 1 embedded BL at 15s, which variation should I use? The most difficult I can do (provided I can hold it for longer than 2X the proscribed time)? Or some easier variation?

Also, my Lsit seems very weak. Should I back everything up to easier variations to help build that up? Or just keep trying to progress as I can?

Thanks in advance for any advice.

For my FSP warmups, I hold an FSP for 50% of the max time for 2-4 sets. For you, that will be something like

flat BL - 3x20s, tuck FL - 3x20s, adv FS - 3x10s, Lsit low - 3x10s

In the WOD, it states that you should use a progression that you can hold for the required period of time.

My L-sit is pretty weak as well, but it's due to bad flexibility and a comparatively weak core that can't compensate for the lack of flexibility. I'm trying to correct it with regular stretching and extra ab exercises like body lever (dragon flags), hanging leg lifts and just L sit holds. If it's your shoulders that are weak, you can add the ring support position to your routine of FSPs.