First let me say thank you for your service to our country.
I can't see a problem as long as the roof rack is properly installed and the yak is properly secured for transport with front and rear tie downs.
How are you planning on transporting your yak at your next duty station?
Is the Navy moving your car and yak along with the rest of your household goods? How long are you going to be at your new duty station? Will you be able to buy an inexpensive trailer there that you would be able to sell when you left?
Now for here in the states, if you bought a trailer is there somewhere that you could store it while you're overseas?
Well thank you, but its actually my wife who is the service member.
We are able to take our car with us so we will use the rack system. The Navy will send the yak as household goods because its under 14' and doesnt have a trailer. The car I am assuming will take much longer to get to England. Buying a trailer in England may not be a bad idea because we will be there for 3 years. We will just have to see what we can find when we get there.
We are only in the states for a couple more months so it may be a waste to buy one now because we will not have a place to store it.
In the short term I may rent a trailer to go get the kayak since its such a long trip. I will use the rack for around town trips...