Proxies in Friday Night MagicTG?

I know in big time facilities where there's a turnout of more than 20 people there is usually stricter rules, however I play at a small time comic book store where the turnout is no more than 10 every Friday. I was playing for the second time there and I noticed this guy was using Caw Blade. His Birds of Paradise and many other cards were proxied, and others he had painted over on the artwork with Yugioh crap and half naked anime girls that looked like they were 8. After the match I asked my buddy who got me into this how he was allowed to do that. He said that proxies aren't supposed to be legal in standard matches in FNM but the shop owners didn't mind but warned me that overusing proxies could piss people off and if a complaint reached the shop owner that he may ban proxies or start banning people who overuse them. So my question is would it be alright for me to proxy like 5 cards for this artifact deck I'm making? It's not like I'm proxying because I'm lazy. I've worked my *** off to get these cards and now I'm only a few away and I'm so eager to use this in a match. If I can't find the cards to trade off someone in the next week I'll just buy them online. This guy however has made no effort to complete his deck as I've been told he uses same deck almost every Friday.