Don't pay attention to slip too much, just speed & handling. Generally, the bigger the prop, the harder to plane. My 32p won't stay on plane till 25-30 mph, 28p planes @ 20-25 mph- tabs up, but the 32 is about +10 mph cruise @ 3500-4000 over the 28. I like being able to pass boats just cruising then stab some boost as I blow by!
Labbed props don't make much hole shot difference that I'm aware of.

Yea I've got a labbed 30 to test too. I am going to run the 30 and the 28 this weekend back to back and then take that data to my prop guy. He is telling me my speedo is about +two mph off.

I would get an accurate GPS speedo asap!

When doing prop testing, I usually use both my lavorsi in-dash GPS speedo, my Garmin chart plotter GPS speedo, and a handheld GPS speedo... just to make sure I am getting accurate data.

I also use both the analog tach, and and the digital Smartcraft tach... to make sure my rpm's are accurate.

Accurate data produces accurate numbers that can usually be improved upon.

If you have inconsistant numbers... it is hard to tell what is real... and what is fiction.

Fiction is hard to improve upon.

Chris

If that 30 doesn't work & you need a 28, I'd love to work a trade deal.