First Yasso 800: Advice needed

I've been following the Break 4 Hour marathon plan from RW-which is my reach goal. I'd be happy in the sub-4:20 range but this is a nice structured plan with good time goals and incentives for me to try to hit. I've hit all the running distance/pace goals except for a few of the Sunday long runs past the half marathon distances (3 of those runs were in the range of +24 second/mile to +60 seconds/mile more than my goal pace). Most of these long runs are 45-60 seconds faster per mile than the times from my training for my first marathon last year (yay improvement!)

I've never done Yasso 800s before so I'm hoping to use this to really get a sense of what my goal marathon time should be. Wednesday I'm doing 9 total miles (warm up with 2 miles, 6x800s, then cool down with whatever remaining miles) and it's given me a goal of 3:57 per 800. Anything I should keep in mind during the Yasso 800s? I'll set my running watch to automatically record my 800x400 times (nike watch does auto loops if I set it up in advance) so that won't be an issue.

Thanks