Because of the mass of the wheel and tire, it can be hard to notice when you simply put it in the bike and spin the wheel. If you set it up so you can tighten the skewer while it's off the bike, then you can turn the axle instead of the wheel and very easily feel the difference.
You can easily make something or find something to play the role of the dropouts. A couple oversize nuts or cut some thick wall pipe, or use a pair you cut off a wrecked bike frame.