This is not unreasonably unfair to the teams in the pool of five. Presumably, the 17th seed is in that pool which ought to be easy victories for any team that has a chance at finishing in the top two of the pool. There could be a problem, however, if not much is known about the teams, and the seeding is very inaccurate.
A possible nightmare occurs if there is a three-way tie for first, thus relegating a team with one loss to finish out of the top eight. This is a serious problem for which I haven't come up with a satisfactory solution (except for some sort of cross-over between 2d and 3d place teams the next day).
The schedules for five and four-game round-robins appear in Tables 5.1.1 and 4.1 respectively. You could simply give each pool two fields, and let them go at it. This would take up eight fields. A better schedule might be one below:
Fields: 1 2 3 4 5 6 7
9:00 D1-D3 D2-D4 C1-C4 A1-A3 A2-A4 B1-B3 B4-B5
10:45 D1-D2 C1-C3 C2-C4 A1-A2 B1-B5 B2-B4
12:30 D3-D4 C1-C2 C3-C4 A3-A4 B2-B5 B3-B4
2:15 D1-D4 D2-D3 C2-C3 A1-A4 A2-A3 B1-B4 B2-B3
4:45 B1-B2 B3-B5
Note that the round-robin for two of the pools of four (pools C and D in
this example) are played over four rounds on three fields. They could be
played on three rounds on four fields, but there are two disadvantages of
that method. First, it takes up an extra field. Second, the teams in the
pool of five (pool A) would be done after the third round while pools A and
B still had two more rounds to go. The schedule above uses less fields and
keeps more players around. The schedule for Pool B tries to mimic pool D,
for the same reasons, but it's kind of awkward.
If you are simply running an 18-team tournament, without having to worry about teams qualifying to the next level, you have all kinds of flexibility. An easy format for the second day for the top two of each pool advance to a quarterfinal single-elimination, and the next two (third and fourth place teams) of each pool advance to a "Division II" quarterfinal single-elimination. (This 16-team Division I & II elimination is shown in Section 16.1.) Schedule the two remaining fifth place teams for a game on the second day, also.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
- - - - - - - - - -- -- -- -- -- -- -- --
1 - 16 2 5 8 11 14 17 3 6 9 12 15 B 4 7 10 13
2 - 15 1 4 7 10 13 16 B 5 8 11 14 17 3 6 9 12
3 - 14 17 B 6 9 12 15 1 4 7 10 13 16 2 5 8 11
4 - 13 16 2 5 8 11 14 17 3 6 9 12 15 1 B 7 10
5 - 12 15 1 4 7 10 13 16 2 B 8 11 14 17 3 6 9
6 - 11 14 17 3 B 9 12 15 1 4 7 10 13 16 2 5 8
7 - 10 13 16 2 5 8 11 14 17 3 6 9 12 15 1 4 B
8 - 9 12 15 1 4 7 10 13 16 2 5 B 11 14 17 3 6
9 - 8 11 14 17 3 6 B 12 15 1 4 7 10 13 16 2 5
10 - 7 B 13 16 2 5 8 11 14 17 3 6 9 12 15 1 4
11 - 6 9 12 15 1 4 7 10 13 16 2 5 8 B 14 17 3
12 - 5 8 11 14 17 3 6 9 B 15 1 4 7 10 13 16 2
13 - 4 7 10 B 16 2 5 8 11 14 17 3 6 9 12 15 1
14 - 3 6 9 12 15 1 4 7 10 13 16 2 5 8 11 B 17
15 - 2 5 8 11 14 17 3 6 9 12 B 1 4 7 10 13 16
16 - 1 4 7 10 13 B 2 5 8 11 14 17 3 6 9 12 15
17 - B 3 6 9 12 15 1 4 7 10 13 16 2 5 8 11 14
1- 2 3-17 4-16 5-15 6-14 7-13 8-12 9-11
1- 5 2- 4 6-17 7-16 8-15 9-14 10-13 11-12
1- 8 2- 7 3- 6 4- 5 9-17 10-16 11-15 12-14
1-11 2-10 3- 9 4- 8 5- 7 12-17 13-16 14-15
1-14 2-13 3-12 4-11 5-10 6- 9 7- 8 15-17
1-17 2-16 3-15 4-14 5-13 6-12 7-11 8-10
1- 3 4-17 5-16 6-15 7-14 8-13 9-12 10-11
1- 6 2- 5 3- 4 7-17 8-16 9-15 10-14 11-13
1- 9 2- 8 3- 7 4- 6 10-17 11-16 12-15 13-14
1-12 2-11 3-10 4- 9 5- 8 6- 7 13-17 14-16
1-15 2-14 3-13 4-12 5-11 6-10 7- 9 16-17
2-17 3-16 4-15 5-14 6-13 7-12 8-11 9-10
1- 4 2- 3 5-17 6-16 7-15 8-14 9-13 10-12
1- 7 2- 6 3- 5 8-17 9-16 10-15 11-14 12-13
1-10 2- 9 3- 8 4- 7 5- 6 11-17 12-16 13-15
1-13 2-12 3-11 4-10 5- 9 6- 8 14-17 15-16
1-16 2-15 3-14 4-13 5-12 6-11 7-10 8- 9