Ran a little test on my own thing a while back and the boring answer was that neither one did much until there was a reason to give. What changed it was posting the plans for a project and saying the file was up for backers only. People don't tip a tip jar, they tip a person who gave them something first. The tip jar still sits there and still gets a few bucks here and there but it's never going to carry the channel. Memberships need a steady reason to stay, and honestly you might have picked the harder one to grow cold. Four months is also not that long, for what it's worth.

Did @john648 ever figure out the real cost per job?

My cousin did this exact thing to his GTI and the strut actually punched through the mount. Took out the top hat and part of the fender liner with it. He was on the highway when it let go too, said the car started wandering and he pulled over to find the wheel sitting weird. Cost him way more than the springs he saved on. Four months is about right too, they just die slow and take everything else with them.