First off, 484 AND 488 were rolled into the shop this afternoon while I was out chasing. See picture
I don't know how much of that I can answer, but...
"It sounds like 4 locos for the current schedule is a ballancing act (I guess last season's three locos at start up was worse). "
-I would say 4 is an absolute minimum. With only three, too much maintenance has to be done at night and on a fast turnaround. You should witness the scramble to get a boiler wash done in time to get steam up for the next day. But, as i said, with four under steam and all still needing things fixed, there is still somewhat of a scramble.
"For the current operating schedule:
1) are five servicable/operable locos reasonable?
--If it were my decision I wouldn't settle for fewer than six. It just makes other-than-routine maintenance a lot easier.-
2) can 5 handle charters or chould a sixth loco be available?
-- Same answer as 1 --
3) would a seventh or eighth loco (i.e. 483 and/or 492) help?
- I sure hope so. It would make extra trips and more charters a real possibility.
"4) would the same seventh or eighth loco make the routine maintenence more difficult (i.e. too many for the shop crew to turn around without increasing shop crew size)? "
-- I think the shop crew will have to increase gradually to handle a 5th and 6th, and moreso for a 7th and 8th.
"On a slightly different line, Has the "Train to Cumbres and bus back trips" hurt the Osier round trip loadings or has it actually helped the bottom line? "
- In talking to those who count the beans and in listening to how many (few) short trips are sold, I'd say it's probably a PR boon and is not hurting the bottom line.