I would advise not to use mesh. Makes no difference whether its driven on the road, beach or in the sky. There is still dirt particles in the air and that will soon turn into grinding paste going into your cylinders and increasing bore/ring wear. It's a stupid idea not to run an air filter, they pose very little restriction these days, although piping does play a factor, roughly every 90 degree bend equates to a loss of 3% peak power.