I am playing a 4 bar chord progression but want to record a solo overdub that lasts 8 bars. I have tried to do this but I am still in the middle of recording my solo as the original loop finishes and therefore it starts playing itself back, which interrupts my overdub.
On the Ditto Looper the max recording time is 5 minutes and the number of loops is unlimited. Of course, the first loop determines the length of the following loops. This is normal because otherwise your second loop could potentially record over onto the silence from the end of the first loop.
Therefore, instead of recording 4 bars of a chord progression, try recording 2 times 4 bars and thus you will be able to record an 8 bar solo overdub.