It becomes a RIP OFF when you were told you would have to rent the car for a week and that week becomes 4 months.
I don't care if it's Berry, Searing, Gina or RKC if money is exchanged, a deadline is agreed to that person should be good to their word. (period no excuses)
Now if RKC told the OP that he is swamped with work and that it could be anywhere from 2 weeks /6 months before he get around to doing his rails then the OP would not have a leg to stand on here.
However I take it a real deadline was given by RKC and if that's the case IMHO RKC should be a man of his word.