Trying To upload SSL certificate to Asus RT-AC87U Router

[Hec]

I originally tried finding a solution for the "There is a problem with this website’s security certificate." when I go to the routers Login Page. I have it set up to use the https. I found this page "http://www.rickygao.com/how-to-upload-ssl-certificate-to-asus-router/" So the questions I have before starting this is.

With OpenSSL I plan on making a certificate. But what is the max size of certificate that I can make, can the router take a 8192 or is the max size 4096? Then do I put the *.crt and the *.key in the same :/tmp/home/root# cat >/etc/ directory after SSH'ing in with puTTy?

The OpenSSL commands I would use:
genrsa -out root.key 8192 -sha512

{Generating master certificate using this key}
req -x509 -new -nodes -key root.key -days 580 -out root.pem -sha512

{Generating the server key}
genrsa -out server.key 8192 -sha512

{Generating a certificate signing request (CSR)}
req -new -key server.key -out server.csr -sha512

{Generating your certificate, signing it with the master key:}
x509 -req -in server.csr -CA root.pem -CAkey root.key -CAcreateserial -out server.crt -days 365 -extensions v3_ca -sha512

If there are any OpenSSL command mistakes that anybody sees, I'd appreciate being told that as well.

-Thank You In Advance