let me offer an alternative
i was in you situation not to long ago
i had the 85L & 135L and I just wasn't using them - but I used the 135L at indoor hockey games occasionally because there SS=1/1000
i shot weddings then with 5D3s and sports / wildlife with a 5D3 & 7D2
for weddings i became a 24-70 F2.8 & 70-200 F2.8 IS with a fast short FL prime when it got dark
if i had some short weddings that were outdoors in good light, i would bring out the 85L to get a few shots (they are incredible and it made me more sad that I wasn't using either of these magnificent lenses
the Sony A7Rii was announce - IBIS, amazing sensor, Metabones adapter with good AF promised (but we weren't going to know until launch)
i got one of the first cameras with the single goal of using the 85L and 135L with this camera - except on day one these were the two lenses that didn't work
Metabones has updated the firmware a number of times and both these lense work fantastic - like native glass - the 135L can be shot at 1/20th and it will be sharper than it will ever be on any canon body - especially if you jump into Magnification mode and do a tiny manual adjustment to nail the focus exactly where you want
i would highly, highly recommend you go down to your camera store, test out either the A7Rii or the A7ii with a Metabones adapter and your 135L - it will put a smile on your face to be able, even with your hands, shoot at 1/20th with IBIS stabilizing the lens - it is like magic
I have 2 5DSRs now and a 7D2 and an A7Rii
- I only us IS lenses on the 5DSRs, usless I'm using a tripod, and I have moved shooting my 85L & 135L exclusively to the A7Rii
Hockey and wedding photographer. Favourite camera / lens combos: a 1DX II with a Tamron 45 1.8 VC, an A7Rii with a Canon 24-70F2.8L II, and a 5DSR with a Tamron 85 1.8 VC. Every lens I own I strongly recommend [Canon (35Lii, 100L Macro, 24-70F2.8ii, 70-200F2.8ii, 100-400Lii), Tamron (45 1.8, 85 1.8), Sigma 24-105]. If there are better lenses out there let me know because I haven't found them.