A dilemma we have. One Non-Normal checklist says to use flap 20 for landing (LE) and the other to use flap 30 for landing (Gear up). However as I am paging through my QRH I see no reference to LE up and TE 30. Therefore I have no Vref speed for final approach if I use TE 30, the only reference I have for LE not in extended position is TE 20 and Vref 30 + 30 for landing.
However I have had simular problem in the Sweatbox you are describing, but there was only hydraulic problem and we extended both the LE and TE flaps on the alternate system even though the checklist said only to use flap 20; this was done, like in your problem, because we had one gear up and wanted to land as slow as we could. We got no comment's from the allseeing god, that sat behind us
In my view: Use flap 30 for landing if having gear problem, even though one has to use alternate flaps.
If no LE, use flap 20 and Vref 30 + 30 as QRH says as we have no other speed reference in our books.