The audio inputs have super flexible gainstaging, and are made to handle eurorack oscillators as input (It suggests using an external oscillator on page 76 of the manual) Eurorack oscillators are typically ±5 volts, so setting a linear value ranging from -5 to +5 will be safe.
Here’s an old thread where some elektronauts routed the cv outs throught the inputs and make a kick drum. They only use 0 to +5, but going all the way to -5 would allow for more headroom. I’ve done it before, and it doesn’t hurt anything. 
My question is whether the V/oct or Hz/V settings can be made control the LFOs in a useful way or not. I’d guess they won’t scale properly, but it’s definitely worth trying.
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