another idea...
on an icefishing website that i'm on, they have a yearlong online tournament. heres how they do it. they give you a card to print out, which is different every year, and you have to put the fish with a yellow tape stretched out next to it with the card, and take a picture, then take a picture of your self holding the fish on the ice (in this case it would be on the water). then submit it on the online forum. this works great for people who want to release a fish. maybe you can make a printable or mail out tape like you said and just have people take pictures of the fish with your tape. the only problem with doing it this way is, everyone has to have a digital camera and know how to upload pictures, also whoever is the weighmaster, or judge, will have to spend alot of time figuring out which fish won because it will take a long time to look at all the tape measures in pictures, with crooked angle's and people who dont put the tape exaclty at the fishs mouth. the fish will have to win by length also. there will be a delay in results.

heres how the icefishing website does it.
i didnt enter it this year so heres one of my friends.




how ever you decide to do it good luck!