Colin:
If you suggested two extender to the 70-200mm. for sure it worth a look on it.
I already push my ISO to 1250 with f2.8 when shooting ice rink now. Acceptable. that's why I afraid losing the f2.8 and going higher ISO.
May be I should try higher ISO first and see how the image will be affected.
Extender is not that expensive, it is just don't want to buy it and later put it aside or re-sell it if it cannot serve my 100% purpose.
hoping some people will response too.
Fun to be here.
thanks,
Bill