Fixed seat rowing geometry is a tricky business, with a lot of different ideas as to what is "best". Even given similar body dimensions, different rowers will find various setups more or less comfortable. Throw in differences in body size and proportion, and things get even more resistant to hard and fast rules. At least with your Chester Yawl, some adjustability is built into the design. Here are a few of my further thoughts, with the caveat that my rowing eperience does not include a CLC Chester Yawl, not that I haven't lusted after one. <;-)
I think the starting place has to be the location of the after edge of the rowing thwart or seat in relation to the oarlocks. I think the reason for that is that most of us would want to row with our buttocks resting on the seat just forward of the after edge, in other words, with our weight entirely on the buttocks and not at all on the thighs. I've seen diagrams calling for the distance from the after edge of the seat to the oarlocks as anything from 8" to maybe 13" or more. For a tall person with long arms, the higher end of that is probably better, but remember that we can only effectively use just so much of the potential range of motion of the oars, regardless of the individual rowers "length of reach".
It is quite common to see folks, especially in boats with shorter oars, trying to get too long of a stroke for effecient rowing. I used to row a Sea Pearl 21 sailboat as auxiliary power, and, even with the ten foot oars on a five and a half foot spread at the oarlocks, I could grab a longer stroke than was good for me, despite the fact that I am neither very tall (5'-8") nor particularly long of arm...plus which I am a bit thick in the middle. Probably a bit thick in the head, too, but I digress....
Back to your question, where your knees land in relation to the oarloks maybe isn't as important as the length of your reach. The idea is to have the seat/oarlocks distance such that the oars come perpendicular to the centerline of the boat (straight out) about in the middle of your stroke without you having to reach too far aft at the beginning nor lean too far back (toward the forward end of the boat--rowing is all about learning to think backwards!) at the end.
So, ignoring your knees for a bit (other than arranging things so they aren't too high), I'll bet you'll find that there is one position of the seat slots which puts the aft edge of the seat about a foot forward of the oarlocks. Start there, position the footrest so your knees don't bend too much when you are sitting with your buttocks/thighs interface at the aft edge of the seat, and see if you can get comfortable getting a good stroke. If you feel like the oars are too close to your chest, move the seat (and footrest) forward a notch. If you feel like you're having to reach too far aft at the beginning of the stroke, move them aft a notch. Somewhere in there you ought to able to find something which works.
.....MIchael