I agree you may have the car too stiff for a street tire, and you may be asking the tire to act as too much of the suspension's compliance. The car definitely looks extremely stable, you're late in and leaning hard ont he outside front in a few places and I never see any yaw in the video? Still, it's hard to tell without seeing the driver's inputs, and usually understeer at 40mph in a 400+ hp car is a driver issue
. Gotta get that outside rear working hard in corners like that, if you're leaning on the outside front you've botched it, usually. It may be that with all that tire under the car you just don't have the confidence to get it dancing, that's a snappy tire anyway and generally speaking, the wider the snappier
My advice, nobody, least of all you (because you've already seen it, Live!), cares about watching the scenery going around track. Point that camera so you can see your hands, preferably synced to a TPS output so you can see what you're doing with the throttle, you seem analytical enough to be able to figure out what works and what doesn't once you can take a look at those "hand-in-hand" so to speak