Jens,
The problem that you have specified is very general and you will most likely need a computer program to evaluate many different schedules and pick out the best. Complications such as the variable number of players who turn up for the evenings play, the possible need for mixed doubles and forbidden matches based on player ability all mean that you are unlikely to find an off-the-shelf schedule. However, you mention that the normal number of players is 25, it just so happens that 25 would be a good number if you were planning on 5 rounds of regular doubles.
Court 1 Court 2 Court 3 Court 4 Court 5 Byes
[(H X) v (M W)] [(E O) v (I L)] [(B Q) v (J G)] [(D T) v (C Y)] [(N V) v (R S)] (A F K P U)
[(I Y) v (N X)] [(A K) v (J M)] [(C R) v (F H)] [(E P) v (D U)] [(O W) v (S T)] (B G L Q V)
[(J U) v (O Y)] [(B L) v (F N)] [(D S) v (G I)] [(A Q) v (E V)] [(K X) v (T P)] (C H M R W)
[(F V) v (K U)] [(C M) v (G O)] [(E T) v (H J)] [(B R) v (A W)] [(L Y) v (P Q)] (D I N S X)
[(G W) v (L V)] [(D N) v (H K)] [(A P) v (I F)] [(C S) v (B X)] [(M U) v (Q R)] (E J O T Y)
In the schedule above, each player plays in exactly four rounds, has four different partners and has eight different opponents. A player's partners and opponents are all different. Furthermore, if you were to divide the players into 5 ability ranking groups as follows:
rank 1: A B C D E
rank 2: F G H I J
rank 3: K L M N O
rank 4: P Q R S T
rank 5: U V W X Y
then the matches are arranged so that the ability differences are small. In particular all matches on the same court are drawn from the same rank groups. The table below gives the matches in terms of groups.
Court Rank Groups
1 [(2 5) vs (3 5)]
2 [(1 3) vs (2 3)]
3 [(1 4) vs (2 2)]
4 [(1 4) vs (1 5)]
5 [(3 5) vs (4 5)]
Hope that helps.
Ian.