Configuring a 4096 bit VPN server certificate

I have been using tomato's OpenVPN server functionality for VPN access successfully over the past few years. I recently had to regenerate server and client certificates, as the previous ones were using MD5 for signature algorithm. New keys are generated with RSA and 4096 bit lengths.

This is problematic when trying to configure the VPN server in Tomato through the GUI.
View attachment 5815
The key is 7875 characters long and when I paste it into the "Server Certificate" field and...

Configuring a 4096 bit VPN server certificate