Jim,
Good for you! Taking on so much of the construction chores is highly rewarding. I've done the same thing a couple times and have picked up numerous skills in the process. Good luck completing it by Summers end...
Ok. Regarding the "ear plugs" I have a suggestion. I have a couple race cars and they both run open pipes. I was turned onto an audiologist. They have rather inexpensive ear plugs that can be molded and extended deep into the ear cavity. I unfortunately have the "gag" reflex (no funnies here guys) with my inner ear and had to shorten it up to prevent that - under $100! My loud cars runs 110 decibels and I have no issue now. Just a thought...enjoy your racing season and use exceptional judgement!
Tony