For quality: 5 stars for availability, 2 stars. As this grounds my Ercoupe because there is no alternative available that is FAA STCd, as an TCs airplane owner it would be reasonable for the FAA to allow my to approve any modification for the design, in order to not suffer unreasonable financial pain... which would be available to me, were the otherwise acceptable airplane airworthiness as an Experimental rules allow,.. by adding the restriction of limitations applicable to Experimental category. This should be automatically available with only simple written letter to the FAA, with no response required and no approval required, other than a copy of the letter be added to the papers carried in the airplane.