I am interested in the Thomasville 1/2" thick engineered flooring at Home Depot. The instructions recommend a Primatech P-210 nailer or P-220 stapler. These tools are typically used for 3/4" solid flooring. Can I use an 18GA Stapler from Bostich, Senco or similar brand? It seems a 15GA staple or L-type cleat used in the Primatech would be too heavy and cause splitting. Any advice?

Ya, I wouldn't use a 15 gauge!!!

I have a HighPro AS-4090 for engineered ½ and greater.

What ever you get, be sure it shoots a staple over 1"

My senco, 1" is the longest staple it will shoot, The same as my PortaNailer 445, 1"

One thing you have to keep in mind at all times.... written manufacturers instructions override everyones opinion, including NWFA or NOFMA guidelines.

I'm with you though, sounds like too much ammo.

15 gauge staple is too hefty for a 1/2" engineered. You'll have puckers in the top layer everywhere there's a staple. At a NWFA class years ago, we were stapling down 1/2" engineered with a Floor Runner. Worked nice. I used my Powernailer Model 200 on some Kahrs. Worked fine as well.