I got really good results on my neopixel blades with the following:
7/8 thin-walled clear blade and tip
TCSS diffuser tube for 1 inch thick-wall blades (same ID as 7/8 thin wall)
3 feet of craft wrap
6 inches of 1/32 packing foam.
2x 'skinny' SK6812 strips (8mm wide, 144 LED/M)
Measure out the strips to ensure they're cut to length to fit the blade length you're going for.
So, put the strips back to back and use clear packing tape to attach the strips to the foam. This helps in making the foam wraps nice and tight. Secure the ends of the foam with clear packing tape.
Put the diffuser tube in the blade (it'll be snug, but moving slowly and with a piece of scrap to help, you can tap it in.)
Drill out the tip so two strips will fit into the tip (remove the mirror, of course)
Roll up the craft wrap and insert into the diffused blade
slide the foam-wrapped strips into the blade, ensuring that they go right up to the drilled-out tip.
This combo results in a bright and even blade that doesn't have any shadows or corncobbing.