Will be putting in 3/4" prefinsihished floor and looking for the size of staple I should use. All I have is 3/4" plywood underneath (+ will add rosin paper) and will run floor strips perpendicular to the joists. Hoping to staple at joists and one in between (avg. every 8 inches). These will be 15.5 guage staples. Do I go with 1.5" or 2" staples? I prefer not to have staples showing in exposed basement (1.5" maybe ???) but will use 2" if it has better holding power (don't see how if there just "hanging out" in basement ceiling). The reason I prefer not to have them hang out below is they would be over my workshop and I store stuff inbetween the joists there and I'm afraid the staples will tear things apart.

THANKS SO MUCH FOR ANY HELP OR COMMENTS. I can't seem to find anything on the web about this except for one comment that they should stick out otherwise they will pull out.

I don't think one will hold better then the other. Just my option though

The 1&1/2" staple will not protrude all the way through your 3/4" plywood. It is the size recommended for nailing 3/4" flooring to 3/4" plywood on a slab. The 2" staple will go through the backside of the 3/4" subfloor a little bit but not very much, 1/8" to 1/4" max. The 2" staple is the recommended length for most installations except over slabs.