Qstor2,
Just keep in mind that the Hiver language is not based on sound. We put consonants and vowels together to form syllables and words; the Hivers wouldn't necessarily be inclined to do that. It may be more like a mathematical progression.
IMTU, Hivers are as old as the ancient Droyne and I treat them similar to B5's Vorlon. For one adventure, I had to create a old Hiver numerical system; the simplest way, I thought, was to base everything on a hexagon split into six equal wedges (the Hiver hand). Each numeric value just added to the previous; zero was a blank hex, one was a hex with one wedge occluded, two was two wedges, continuing in a clockwise rotation. Ended up have a strange system that ends in 21, so I made 21 a mystic number full of strange meaning in Hiver superstition.
Conceivably, the Hiver sign language could have 22 (including zero) "syllables" that can be combined to form words; these would be represented similarly as hexs and wedges. While signing, head wobbles, shakes, nods, neck twists, and even toe tapping or stomps could be used for punctuation; these might be represented in the glyphs as side marks similar to that in the Rikchik language Jeff Z. referenced.
All in all, whatever you decide, it will be an entertaining exercise. Best of luck!