There's a guy on youtube who completely strips his plants back to what looks like twigs at around day 18, but they always bounce back like you wouldn't believe. Some strains really don't like it though and you could cause a hermie issue if you do it to the wrong strain so I'm not saying you should do that I'm just saying what's possible... I'd imagine any strain could handle 5-10% leaves taken at any one time though. Even 5% a day for a week would be fine I reckon.
Your plants look fine though and like Tex said they really just need a bit of a pluck in the middle and down low where the light is too filtered and weak. That's all I'd do.
I don't like counting chickens before they hatch but I can easily see 2 ounces coming off each of those plants if all goes to plan, maybe even 3.
Either way I look forward to see how the rest of the grow goes for you, looks like you know what you're up to for sure.