I wear a full cap and the first one I bought, it was a complete disaster.

Mine was 70% density and I cut it to 1 and a half inches in length, and that was way too short. It just didn't look right, AT ALL. The hair wouldn't 'lie' right on the top and sides and the back stuck up.

Now I get my caps at 55%, and leave it around 2 to 3 inches in length. I think 45% might be too thin, but it all depends how young or old you are.