So I just took delivery of my new 5.5m.
Looks sweet.

But...I have my Naish pump that came with my S25 Wing. Thought that pump with its valve fittings would do the trick.

But it seems the Armstrong valve is just a shade smaller in diameter than the Naish valve.
So air leaks slightly as you pump up the wing .

Result = the pump doesn't read the PSI pressure correctly so you keep pumping & pumping waiting for the gauge to register pressure...

This could result in an over pressure & burst bladder.

So...am I missing something here??

Please enlighten me!

When's the Armstrong B wing coming out ? Yeh

pump till your needle hits 7 psi. disconnect pump and check wing tip to make sure you cannot fold it. should be good.

All jokes aside many people using inflatable kites and wings just pump it up to the feel and don't bother with reading the guage.
It should feel nice and solid with little to no give around the center of the leading edge. Give it a flick with your finger and if it makes a nice ping she's good to go .