The problem is not just the corner but also a horizontal notch would have to be cut to clear the rear bottom lip that was added by Norm in order for it to close.Hey Gadget, I was thinking about this just now and realized Norm might have radiused that corner to prevent cracks on the GRP, it is a material that's kind of prone to cracking... I believe you'd be better off radiusing the matching part of the targa bar, rather than squaring off the top. Food for thought. Have a great Monday, cheers.
In terms of aesthetics I "think" that would look off because the bottom edge of the main top would be lower than the bottom edge of the targa bar where the two meet.
Also, having the front edge of the targa bar close against the existing weatherstripping when you shut the trunk sounds like a safer idea than having the bottom edge of the targa bar come even close to making contact with the rear lip of the hard top. Especially as our trunks have some "squish" upon closing.. Push down a little too hard and the two parts are making contact at speed.
At least that is my logic so far.