In reply to Philip:
Disregard if irrelevant now but you can definitely fit more than two bikes in the bike area the Class 170s that run that route, bear in mind this is also the wheelchair space who always get priority, however the guard won't mind standing with your bike in the vestibule if you're sensible and polite. Also most of them run as 3 cars now.
One thing to bear in mind is the route is very busy Fridays to Monday in summer due to weekend trippers to Skeg so I'd avoid these days (especially Friday and Monday), they may run as a 4 or 5 car to mitigate this but it's not guaranteed.
Source: I work for EMR and commute on this line.