What's your tuning? I have an RGD2127z and I use the D'adarrio 8 string sets on it (lowest is G, then dropped C from there) and the strings are plenty long enough. Maybe look at the baritone sets and add a string?
You know, I'm not going to hate or target you for neg. rep. if you leave your name. I'm sure I can find plenty of other reasons to hate
Stop calling it detuned. It's tuned, just not to standard. It's not a ....ing DeVries.