They are usually quite busy through to EXD» from Exmouth, but then you could probably live with putting 1 coach on with room to spare from EXD onwards. Different story at other times (the last one out of EXD last night was full and standing with bikes too), so I think at the moment the set structure/schedule is just about right, even though it would seem to be a bit inconvenient for customers in terms of timings. Summer Saturdays could be interesting though come some nice weather.
most weekend trains seem too busy for 1 coach, not sure about weekdays.