Hey mate, I have an '06 Menace 12m so I should be able to offer some help.
The two-pump type system they use isn't the best as the 'airline' you're referring to tends to kink between the main part of it and the connections to the struts. The main thing to check while inflating the struts is that once you have inflated your kite to the pressure needed check that all the struts are fully inflated. A kink in any of these connecting sections will leave a strut un/under inflated and then the air can slowly leak in causing the other struts to depressurise.
Let me know if you need any more help on this mate

D