I have an 8" Duravent chimney with a ceiling support box I need to connect an oil boiler to. The Simpson distributor is telling me to just shove the pipe in and use strapping to hold it up? Is this legit? Shouldn't there be a thimble that I can screw the stove pipe to? They told me that they don't make the snap lock adapter any more and that even if they did I should not use it for the oil boiler.