Once you understand how oil filters work, you'll see why size isn't really an issue. 
If you were to slice an oil filter open into circular segments you'd find it looks like a donut inside. There's an outer ring and an inner cylinder, separated by the filter element. The oil flows into the outer ring, through the filter element into the center, and back out to the engine through the center. The filter is definitely not the restrictive point. You could put a HUGE filter on and it wouldn't make a difference, since the oil still has to flow back into the engine through that fitting the filter screws onto. That's the restriction. As long as the filter allows enough flow to keep up with that, you're fine. It'd take a tiny filter for size alone to restrict that much. That's why the filter medium and it's flow efficiency is the important thing. If the filter medium restricts flow, THEN you could be in trouble. But most oil filters have valves that will bypass the filter medium if filtration becomes too restrictive, so even that's not a huge issue. Obviously circulating unfiltered oil isn't ideal, but it's better than starvation.
Here's a good diagram showing oil/filter flow in case my description wasn't very good.
