I have an Omega D2V and had the same problem briefly. your choices are to prop up the easel as you thought or use a larger lens like you said. I used a 75mm lens (135mm might be overkill as you'll have to raise the head even higher, cutting down on the light). Both systems have worked for me.
If you do prop up the easel, make sure it's level with the base board, (or 90 degrees to the lens). I found out the hard way when one side of the first print was blurred. After a couple of minutes scratching my head, it dawned on me.