One suggestions Spriggsy -- you want want to get in the habit of making your padding AS STRING * SIZE. Here, it's not going to matter as it's just unused padding, but getting in the habit might keep things standardized for you in the future if you need some odd size padding.
Say for example that the data structure is an integer, then a byte, then a long.... You'd need padding after that byte, and it'd need to be 5 characters worth. Can't use a LONG for that, but if you're in the auto-habit of typing PaddingX AS LONG, your brain might automatically insert that into your code, and then you'd have the dangest time finding and fixing that type of glitch as your eyes will just skip over it, as your brain assures you, you've already made the adjustment there... (Trust me, I speak from experience, as I've spent many an hour not being able to find such a simple problem in my own code!)
What variable type you use for the space isn't really going to matter to the code -- be it 4 bytes, 2 integers, 1 long, a single, or a string * 4 -- but the habit of typing out the length manually might save you some serious debugging issues in the future. (And besides, it'd allow for an uniform padding syntax so all the code ends up looking the same.) ;)