letsencrypt shellinabox

I see this problem all over the internet searches, and can't seem to find the resolution. I want to use shellinabox on whatever.net:54321 I have letsencrypt certificates I've tried to copy /etc/letsencrypt/live/whatever.net/fullchain.pem to /var/libshellinabox/certificate.pem then chown shellinabox:shellinabox certificate.pem, but after trying to connect from a browser, SIAB creates a self-signed certificate-whatever.net.pem I've also tried editing /etc/default/shellinabox certdir line to point to /etc/letsencrypt/live/whatever.net, but then shellinabox compains about not having correct file permissions. (Understandably so) I've also tried copying /etc/letsencrypt/live/whatever.net/fullchain.pem to certificate.pem, and chown certificate.pem to shellinabox, but that doesn't seem to do the trick either. Seems like it should be easy enough, but no matter what I've tried, letsencrypt still wants to make it's own self-signed certificates, which causes browsers to complain. So, the big question, what's the magic tapdance to make siab use letsencyrypt certificates and stop making self-signed certificates?