Just to clarify - it is a legal requirement to carry the aircraft flight manual or equivalent document on all flights (NCO.GEN.135)
...so I spent a rainy day .pdf-ing our precious original for our PA28. I then printed it out in A5 and put it in a binder, for the seat-back pocket. I weighed it. It's 1.5lb. Technically, I should now include this in the W&B basic aircraft weight. We're having a re-paint this year and a re-weigh and I'll certainly include it then.
Actually, I could just keep the .pdf in my phone, but it'll make it a bit hard to read when we're on fire.
TOO