Convincing parents about a tattoo?

ok so i turn 16 soon... and i really want the roman numerals for 11 as a tattoo, i cant explain how much the number means to me... but i really want it on my birthday this year which is 11/11/11 so i feel if anytime i should get this tattoo then! on my back to cover up a scar that i really hate (only small about 3cm by 3cm) but the thing is they dislike tattoos. im not someone who will in 10 year look back at it and say "i regret this either" ive been brought up in a family not keen on tattoos, yet ive always loved them, and thats not going to change, im 100% sure of it. any ideas?