I managed to finish round 4 yesterday. It's a good thing I had the day off. Round 4 ended in a similar manner as round 3. That is, split chain, split ring, start round 5 with split ring. I like this doily. It will be a nice break from making horses for my carousel.
I was afraid that the size 100 was going to be hard to work, but after round 3, I see that it is not. It is not a lot smaller than size 80. That is a good thing because I spent a good part of round 3 untatting. There are 2 different rings on round 3 and I kept getting them confused. I would catch myself after about 4 stitches, which meant take out 2 stitches and add a picot, or take out 2 stitches and remove the picot. I finally got it right. Undoing a few stitches was not particularly difficult.
Another thing I had to manage was when I started a ring or chain. Getting the first stitch to snug up to the previous element was sometimes a minor challenge. Of course, if it left a gap, I took that out and fixed it. The real fix, for me at least, is to start that part with a 2nd half stitch. Take for instance, at a thrown ring. I stop the chain, loop the 2nd shuttle thread to make the ring, and the first thing I do is make a 2nd half stitch. I do not count it. I make my ring, then change shuttles to continue the chain and make a 2nd half stitch, then finish the chain. For some reason this keeps things tight, no gaps. I don't think the extra half stitch affects the count.