Just watched 10 mins of footage from the game.( May 1987)
Checked official attendance 18,413..if that's correct I don't see now whu would have had only 15k home fans for an end of season match where Billy Bonds and Mark Ward were presented with awards..Whu were a half decent team ,the fans cheered the team off at the end and were still on the pitch when the home players came up into the stands to show their thanks
You can hear chants of City City, quite loud ..if I were to guess,the whu rush on the away end happened well after the pitch invasion to applaud their own players,and that must have taken half hour at least.
I'd say 2k ,maybe just over is about right and West ham were not the sort of club to pander to away fans 're ticket allocation anyway.
I did use to know a lad who worked on their turnstiles tho,he never seemed short of cash lol ;)