A 3L Platypus is pretty light (1.5oz).
Me--- I would be wary of just taking that. I use one 2L platy and two 1L platy’s. Most of the time the 2L is empty. I use it at camp though. If one bottle leaks, no problem; I still have a fall back. This principal came in handy during Easter vacation as I backpacked Wisconsin’s Kettle Moraine South Forest. One of my platys leaked all over inside my backpack. At least I still had 2 more containers to carry water.

In another situation, my hiking partner had his 3L bladder filled. Unbeknownst to him, the drinking tube came unscrewed at the platy. He thought he was just sweating on the back. No, he was leaking his whole water supply! That hurt. Us other two shared water with him and we didn’t make it to a stream that day. So we were all a little dehydrated. Miraculously it rained during the night of which we collected rain off our tents.

I may be overdoing it, but my mind is at ease with at least 3 water bottles.

-Barry