Yeah, weighing after a feed is the worst time for consistency or accuracy. Prey size varies as does digestion time and how much they may have peed or pooped. Day before a feed is better as they're done digesting and may have pooped too, but if there wasn't a poop that week it will be an inflated measurement which is something to keep in mind.
I pretty much only weigh for records purposes when I find a poop and it looks like they're "empty". Sometimes at sheds, though most of mine don't bother pooping after a shed and do that whenever, so that isn't often the empty weight for me.
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