Park/MH Insurance

I have a 20 space mh park and I own 15 of the mobiles. I payed off all the M.H. I only have the mortgage payment on the dirt. I dropped all of my individual mh insurance policies and just carry a 1 million dollar blanket policy. They are all early to mid 90’s 16 x 80. I am in a position to self insure. Am I making a big mistake in my risk management?