Can you tell by the size of the envelope from OFA if your results are passing or not?

Yes.
Big (certificate size) passing
small, legal size, not passing or all prelim's

Yep...
One is your certificate (large]
or One is a letter (small)with the disappointed news..

Mine...large...prelims...bad news....

large as in sqaure, certificate size....not legal, legal size is not good if they are over 24 months.
Sorry for your bad results, we have all had that happen...

All prelims are large - folded in half 8.5 x 11. Sorry if it was not good news