a radius cut is a curve, not an angled cut

Usually the units do not require any other support. Some have clamps to hold them in place, some dont use them

Why are you having doubts about what your fabricator is telling you? He's 100% correct.

new-beginning: yes, of course, I wasn't thinking, duhhh. Sorry - my only excuse is that I'm fatigued.

weedmeister: thank you, reassuring to know.

hollysprings: I guess because I am a stupid over-thinker!

Here it is 2020 ... and your post was exactly the info I wanted to understand today! Those of us not in the business don’t know the lingo ... and dumb us for wanting to understand and get reassurance that what we are being told is “right”. Thanks for asking the questions!!!!

Kathy:

There should be no "straight cuts going over each other" on cooktop cutouts. There should be a slight radius in the corner. A good fabricator will knock the meanness off the fresh cut edges, top and bottom. This eliminates stress risers that when heated can become cracks.

The cooktop and countertop should be installed per the manufacturer's instructions. No additional support is necessary.

Thanks Joseph. The product I selected was quartz with eased edge. I did not like the location of the seam proposed - it was just to the left in parallel to the sink. I asked to have it moved to under the cooktop on the one side of “L” shaped countertop (other side has sink and dishwasher). The updated design was to have cut outs at each side of cooktop - basically a separate piece that would connect the two pieces under the cooktop at top and one at bottom - where cooktop would have lip over counter.

From your comment I’m not sure if you are saying this is “bad”?

You should also use some kind of heat tape to protect expansion and contraction from heat . This can prevent quartz from cracking .

It's heat conductive tape and it conducts heat away from surfaces. More important is smoothing the cutout and edges and keepin a radius in the corners.