Everyone said to make your board longer so that you could make a longer leader and I agree with them. I do not think I would go longer than an 8' board to start off with. With an 8' board you can make furled leaders of any length up to 7' and that should take care of your needs for now. You also asked for the spacing between the pegs and like Jack stated, I have tweaked Kathy's formula also and increased the distance between pegs. I like the 40% for the butt section, 30% for the mid section and 30% for the tippet section. On your board the section between Peg 1 and 2 would be the butt section, the section between Peg 2 and Peg 4 would be the mid section and the section between Peg 4 and Peg 3 would be your tippet section. To determine the distance between pegs you would need the overall length of the furled leader you want to end up with and add 10% because you will twist both legs of your leader until they are 10% shorter before you allow them to furl together. My board is set up to make three different length furled leaders. They are: 4' 5", 6' and 7'. As an example the peg spacing on my board for a 7' leader is as follows: Between Peg 1 and Peg 2 is 33", between Peg 2 and Peg 4 is 31" and between Peg 4 and Peg 3 is 30". Those three measurments equal 94" minus 10% equal 84.6 and divide that by 12" equals 7.05'. I am sure that others have a better formula, but, that is mine. If you set your board up for different length leaders, remember that the pin at the 10% will be at different locations for each different length leader.
Hopefully, I have not confused you even more. Just ask your questions and I am sure someone smarter than me will come up with a better answer. I just furnished the above because no one had responded to the second part of your question on peg spacing. Just have fun and remember that furled leader making is addictive!!
Fly fishing and fly tying are two things that I do, and when I am doing them, they are the only 2 things I think about. They clear my mind.