All jokes aside, regarding sloppy boxes!! 
The el-cheapo solution is just layers of Electrical Tape on the sides of the base of the fin... But you only get 1 shot at it. For a tight fit, the tape gets a little squished, so if you pull it back out for a second go, you need to re-do some tape...
So you need to know what position you want the fin, and have the plate carefully positioned... or use a "fabricated paper clip" to help position the plate... or similar...
I have a board with the SLOPPIEST BOX EVER!!! 3-4 layers of tape on each side.
PS - it's not a McTavish... All my McTavish boards have top quality fin boxes which are absolute perfect fits for the fins.
mctavish fin boxes have nothing to do with it. it depends on the fin and brand etc etc more than anything.
bloody mct pimps
Cut a coke can up and wrap it around the base of the fin, or go to KFC and get a plastic straw and cut it in half, both ways work a treat!!
Crap fin take it back to Kmart for a refund.I've never had this issue but all my fins are hand made by WIZ from McTavish fame.
. US boxes are typically shallower and slightly narrower. Therefore US fin manufacturer are usually a bit thin and don't quite fit right in boards made in Oz.
I just cut up a the guts of a plastic softdrink bottle (2 litre is best) in strips to put on one side of the fin (about 10cm x 2cm) or if fin is really loose I cut it wide enough to go under the fin and up both sides, easy as. Sometimes I just put a single strip on both sides. I think most of my boards have a strip in the fin box.
Use some of the expanding dentist tape - Sharpie will know what its called....it works a treat. Alternatively just glass a few layers onto the fin at the base and problem solved. Should only take ya about 2 mins and another 2mins to finish it nicely....then you never have to worry about it again.
and if all else fails, you could scratch around the back of the lounge chair for lose change and once you have $1, you can pop out and buy a packet of the real thing.
I actually find them more useful at the side of the fin rather than the base.
You know what's a hoot.
Read all the instructions and every time you see the word "fin" replace it with "dick".
Ps. I just realised, that's heterosexual smut, yippee, I in front by 2 now 
