Yes it would. We’d probably have to take it to a laundromat or dry cleaner.

that is a very heavy blanket. my DIL wants a weighted blanket and I've suggested that she use the queen size t-shirt quilt I made my son to see if it's heavy enough first. Also, if you double bat it will add weight, especially to a t-shirt or denim quilt.

Quilters Dream makes a heavier weight batting that might work. Or use a double layer?

I once implied to a long arm quilter that when my top was finished I wanted it to be "puffy". She put a double layer of batting in it!! This was a quilt made for a raffle (Lady of the Lake) and was so darn heavy, it was hard to carry or display. Would have worked for someone in Alaska...but not Missouri. I felt that it was ruined.

Think about making your quilt go all the way to the floor. I made a king size like that and it is really heavy. I didn't weigh it but I know it is significantly heavier than ones I use with a bedskirt. He would need the extra length on the sides to stay covered up anyway. I have to take it to a laundromat, takes forever to dry. You might consider just piling on quilts and blankets to get to the weight most comfortable and make a big duvet for the stack. Eliminates the laundry problem and most of the time only the cover will need a wash. If you actually made a 35 pound quilt that would be so hard to move around to put it together and can't imagine try to quilt on a DSM at all. Just making the bed would be a workout.

I also think that making several "heavier" quilts and stacking/piling them on would work better than one really heavy one.

You could maybe attach ties to the edges of the quilts so that they would not slide apart.

A 35 pound quilt would be a monster to try to wash.

You said this person weighed around 300 pounds - how tall is this person?

What size mattress does this person use?

My winter quilt is pieced flannel and it is flannel backed. The batting is Warm & Natural. I do not know the weight, but it is definitely heavy and warm. The heaviest quilt that I have ever used was my grandmother’s polyester double knit quilt.

If you must use a flannel backing, line it with a sheet or prewashed muslin. This way the flannel backing will not wear/weaken from whatever you are using for your weight. Also, you truly won’t need to make that blanket that heavy. I don’t know how you would feed that blanket through your machine.
Look up proper instructions to make these weighted blankets. What are you planning on using for your weight?
As I make many of these blankets, I would suggest poly beads for the weights. Your blanket would be able to be washed in the tub and set outside to dry in the sun.
Good Luck with this project.

I made this type of quilt with the denim circles and can give you the scoop on it:

The denim is very heavy. I wanted a queen size quilt, but ended up with a much smaller quilt because of the weight. In the end, even though the quilt was heavy, I didn't find it very warm (and I get warm easily). What I did find, however, was that it was so heavy, it was hard to move under it. I didn't use any batting in the circles.
The bigger the quilt gets the harder it is to sew together, you will kill your shoulders and arms and need lots of lineament and pain killers by the time you are through (or at least I did)
Make sure you have a lot of either leather or denim sewing needles before you start, because you will break many of them before you are finished

Would I ever make one of these again? Probably not, at least not a circle one for the fake cathedral window quilt, although it is a great looking quilt. I may try one with using squares, because it would only need straight seams, as apposed to the curved sewing around the circles to hold it down.

I just weighed one of my heaviest oversized king quilts and it came in at around 12 pounds. I agree with the others who suggested making several quilts and stacking them. I don't know how you would even be able to quilt something that's equivalent to the thickness of 3 "normal" quilts, and I don't think ties would be strong enough to hold it together.