My R5 arrived on Friday. One of the first tests I was curious about was how good would IBIS + in lens IS be on something like my EF 16-35 f/4L IS. In two different tests, I really did not see much of an improvement over in-lens IS only, getting down to hand holdable shots around 1/8 to 1/4 of a second and not the 1-2 secs I am hearing go by with those using the RF 15-35. Of course, much of this could be the EF mount, fewer connection pins, etc. But I am curious what others are finding with their EF lenses.