As a re-enactor/living history 15 years ago, i always found the Lightweight Ruck more comfortable. That X frame never seemed to work ergonomically on ones back as opposed to the Lightweight Ruck Frame. Admitedly, as you say ref the colours, mine was only 2 tone, yours seems to 5 tone. Very unusual.
I've never understood why the liners weren't simply made of plastic, perhaps not considered durable enough but the British PLCE rucksack of 1989 could be used with purpose designed liners made of clear plactic.
