"Warm deserts" for Environment, same as Camels?
Organization: Solitary, patrol (2-5 on giant striders), band (5-20 plus 1-2 leaders of 4th or 5th level and 3-15 giant striders), tribe (20-40 plus 40-45 noncombatants plus 1-3 leaders of 4th or 5th level, 1 7th level chief and 5-30 giant striders)
All that looks good.
A typical hek stands 4 feet tall and weighs x to x pounds.
Automatic Languages: Common, Hek. Bonus Languages: x.
Terran, Ignan, and Aquan make sense to me.
I like the 45-50 lb weight. Making them 120 lb would push them into the "short but stocky" Medium range, as you say, and I like Small for them.