It's the practice technique...
But really, I pull almost as hard as I can, and I watch to ensure the foam is being compressed the same as the foam next to it. This seems to net decent results. Hard to describe. Fingers suffer. I've tried using fancy upholstery pliers that are designed for pulling vinyl, but I always got better results using my hands (better feel)..
I actually don't care for the xtreme vinyl from YAT, I've used it a number of times, and it's ok... but I think it actually rips too easily. I want stretch, but also durability. I've leaned towards the Wisper from Joannes. Cheaper by far, when using a 50% off coupon around 12/yd (or $36 per table). Plus, no shipping.
I was just in Joannes picking up the spray adhesive, they had some nice vinyl for a lot cheaper than the YAT xtreme. I'll take a look at the Wisper next time.
It did feel like the xtreme was going to tear where i had made relief cuts.