Hi Roger,
this has been discussed in another thread on here of late.. titled (I think) Budget Telephoto. Anyway, in that thread I posted a link to a chart, this one
Sigma MC-21 adapter allow SIGMA’s CANON EF mount interchangeable lenses to be mounted on L-mount cameras (Panasonic S1, S1R).
www.tttphotography.com
I use the MC-21 on S5II and have used it on an FpL. I've tried a Commlite Adaptor in the past but think the MC-21 is probably the better of the two. Definitely an improvement in autofocus operation with the S5II having PDAF but generally it's better to stick with the later EF lenses. I only have two EF lenses left now, the 135 F/2L which is pretty awful and I mainly use with manual focus, whereas my other lens the Canon EF 24-70 2.8 version II feels almost like a native lens, I have used others in the past but now there are plenty of options available in L mount, and my Canon use is now mainly telephoto with RF mount lenses.
You will probably find more answers to your question with a google search or YouTube where there are quite a few videos on the subject, not sure there are many users here.