Yes, Maidenhead to Marlow has to be two car as that's all the Platform at Bourne End can handle. This unit then does the shuttle from Bourne End to Marlow during Peak Hours. The 18:14 from Maidenhead to Bourne End (17:42 off Pad) is scheduled as a 4 car. This also forms the 18:44 off Maidenhead.
The 07:07 from Henley to Pad is scheduled to have 6 cars.
.....Having written the above I have now found this from another topic, this going back from the May timetable change. As mentioned above the 17:42 now has an increase of 1 coach from what is quoted below.
Semi Fast Peak Services Formations > From Next Week
16:42 Bourne End 2 Car
17:12 Henley 4 Car
17:42 Bourne End 3 Car
18:12 Henley 6 Car FX 3 Car FO
18:42 Bourne End 4 Car
19:05 Henley 3 Car
20:18 Reading 6 Car FX 3 Car FO