If you have some decent muscle, and have some cuts (not permabulker)you can run against much bigger guys. I did fine in my time. The key is not to look scrawy. An 18 inch lean arm guy might do some serious damage for a little while with a girl, but girls aren't stupid (well ok, maybe 50 percent of them are). If they are into you as just a pure lust thing for the 18 inch arms, it will wear off quickly. In the end they will leave for a successful guy making money that provides a lifestyle.
Think of it this way. You hit the club and there is this stripper looking girl that has huge boobs, and a perfect body she spends all day on. Is this the type of girl you screw or go long term. To me it is just some messed up girl you screw for a while, and toss out the minute she gets too annoying.