I know labbing can increase top end but what does it do to cruise speed?

i lost 2 mph cruising speed ,30 pitch maximus labbed vs non-labbed

It is possible to loose cruise speed when lab finishing a propeller. As the slip can increase on a lab finished propeller.

Julie

Full blown Labbing will often decrease cruise speeds. However, a conservative formula (blueprinting) can reap acceleration and a slight top end gain without sacrificing mid range cruise speeds.

Higher slip % less efficient deep hull tend to lose the more in the middle with Labbing than air entrapment low slip performance hulls.