Entry form design
The Beanie Baby 5k Run, in Westmont IL, did a good job of designing its trifold entry form. The tear-off portion has no vital information on its reverse side and it can be folded and mailed using a pre-printed return mail flap.
Unfortunately, the 8 1/2 x 11" size does not leave room for a mailing panel, so direct mail forms must be stuffed in an envelope.
Ideally, the form would be printed on 8 1/2 x 14" paper, allowing an extra panel for a mailing label. Direct mail would only require inkjetting of addresses and two tabs to hold it shut.
Still, the preservation of course, registration, and contact information on the portion of the form retained after mailing is crucial so that runners will not lose any valuable information they may need after mailing in the entry.