various things i've learned shooting hockey games
My hardware I use
5D3, 7D2, 70-200 II, 135 F2 L, 200 2.8 L, 100-400 II
- TC works as long as you don't have to shoot through netting - if so, forget about it - you will too often catch the net and miss critical pictures - it is extremely frustrating and if I see a net the TC does not get used ever
- spend a few days watching Youtube videos on Noise Reduction (yes days) and you can seriously improve your hockey pictures at higher ISOs
- unless you are shooting tykes (6-8 year olds) 1/500 is too slow for hockey - I hate using even 1/640 and only if we are talking about gruesomely low light would I even consider 1/640 - 1/800 is not even cool with me but I will accept it and go for images where you are not trying to stop the action
- I start at 1/1000, F2.8, ISO 3200 as a baseline in every arena - a pro arena with good lighting if you slip in the 135 F2 as a non-pro camera, then ISO 2000, SS 1/1600 F2 is fantastic on the 7D2
- i have learned with hockey with lots of practice with noise reduction, masking, etc - to accept up to ISO 6400 so I can use SS 1/1000
- when i experimented with the 100-400 II on the 5D3 at F5 I was shooting at 6400 and it worked fine (this is an attempt to answer in an indirect way your TC question)
- personally, I shoot in AI Servo with BB Focus, I also try and pre-focus as much as possible, and yet if the TC slows down the focus grabbing at all I would rather just crop without a TC
- not sure I have helped at all - other than to say try exploring higher ISOs (which might make your TC work) and up those SS as well
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.