I'll admit I don't understand the grouping for FSPA - I just show up and play
http://www.fspazone.org/rules/current-fspa.html#Selection
But here is a discussion we've had recently on the league email list discussing the grouping of machines. I hope it helps:
"As for the rest of the machines in the set, there's no set rule. The rules mention a "well-defined scheme" which can be anything you like. We use a machine distribution known affectionately as the "grouping thingy", available here: http://www.fspazone.org/fspa-groupingthingy-0.2a.html. Basically, you assign each machine a letter as groups pick them for their first machine, then the other three machines for a given group follow the pattern. You can use whatever scheme fits your league.
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Just to give a little more detail to the previous message... the reason the rules don't specifically address this topic (machine selection for games 2-4 of a meet) is because it's highly dependent on the number of groups you have and the number of machines you have available for play at your location. The machine assignment procedure is going to be considerably different if you have more machines than you have groups (especially if you're fortunate enough to have LOTS of machines to choose from, say a dozen or more), vs. if you have fewer machines than groups (which typically means some groups will have to wait for a machine to open up). Also, if you have less than 4 machines available, groups will be required to play some machines twice during the same meet. There are basically infinite combinations, and we didn't want the rules to be infinitely long so we left it to leagues to figure out a scheme that works best for their particular situation... thus the "Selected machines are distributed among all the groups by the SLO, according to a well-defined scheme" language at the bottom of section 7 of the rules.
If you'd like to use the Grouping Thingy that Dave linked to, let me offer a brief explanation of its use, because it's not at all obvious. Write letters A, B, C, .., one letter for each machine available. As you collect game picks from each group, write those game picks next to the letter corresponding to the group: A = group 1's machine pick, B = group 2's machine pick, etc. If you have more machines than groups, assign the extra letters to machines randomly. Then find the section of the Grouping Thingy that corresponds to however many machines you have. Finally, you'll see columns with groups of three letters (e.g. "BK1", "BK2", "sott(4)", etc) -- these correspond to different algorithms we've tried over time. No choice is "right" or "wrong", so just pick something, say the leftmost column. The letters in that column define the machines that each group will play for games 2-4.
SO, concrete example: let's say you have 10 machines and will be using the leftmost "BK1" scheme.
Group 1 will play: A, E, J, C.
Group 2 will play: B, F, K, D.
Group 3 will play: C, G, A, E.
etc...
(You'll note that the subsequent letters just rotate down the line in order with different offsets; there's no real magic involved.)
Whew. It sounds pretty complicated but actually becomes pretty easy once you've done it a couple times.
Finally, if your league decides to use FSPA rules, one thing we can offer you is your own instance of our Web site scorekeeping system (i.e. what you see at <http://fspa.league.tater.org/>. The site makes it much easier for your league officers to administer an FSPA-style league, and for your players to check results and stats. It also provides fun extra stuff like a badging (achievements) system to help further engage your players.
Hope this helps! Don't hesitate to ping us if we can be of any further assistance, we love helping leagues. "