The turret roof is a lot thicker than it seems after closer inspection.
View attachment 60707
In terms of turret geometry VT4 is a bit better, but overall I think you're way overestimating the VT4's capabilities.
That's what 99A's turret protection module really looks like. Within the white box of picture 2 is the piece of turret protection module. The top goes down to a thickness of zero instead of having any left. The photo is processed due to secret keeping reasons, hope u guys can understand.