United Airlines changed their rules and now they generally don't charge extra for kiteboarding equipment if it is under their limits of 62 linear inches and 50 pounds.
On my last trip the ticket agent asked me questions about what was in my golf bag and I told them and they were going to charge me and then they checked with another employee and came back and said there would be no extra charge. Also, they check the weight more than the linear inches, and I was under the 50 pounds but over on the inches.
Here's the link and the rules as they have them posted on their site as of today:http://www.united.com/web/en-US/content/travel/baggage/sports.aspx
United Airlines will accept one kiteboard or one bag containing equipment used in kiteboarding as checked baggage.
If the kiteboard or kiteboard container is over 50 pounds (23kg) or is greater than 62 (158 cm) total linear inches (L + W + H), a $100 service charge applies each way. The service charge is in addition to any excess baggage charges that may apply, but first or second bag charges do not apply.
If the kiteboard or kiteboard container weighs less than 50 pounds (23kg) and is less than 62 (158cm) total linear inches (L + W + H), the $100 service charge does not apply each way, but, if applicable, the first or second checked baggage service charge applies.
The board must be well padded or the entire board must be encased in a suitable container to avoid scratching. United Airlines shall not be liable for damage to a kiteboard or kiteboard equipment.
Excess Valuation may not be purchased for a kiteboard or kiteboard equipment.
Note: On United Airlines flights, kiteboards greater than 115 inches (292 cm) in length will not be accepted as checked baggage. On United Express flights, kiteboards greater than 80 inches (203 cm) in length will not be accepted as checked baggage.
Kiteboards are not allowed during excess baggage embargo periods when no excess baggage is allowed. Kiteboards will be accepted to Costa Rica during an embargo period.