Here are two sill tanks I had made for the 110 - capacity 55l (drivers side) and 35l (passenger side). Simple design with less capacity than Erich's above as they don't wrap arount outriggers, which I didn't want as I thought it wiuld be difficult to clean mud etc from there. Dimensions (length) could probably be increased for a 130 - not sure of available clear space in 130.
Filler was installed separate to original although original (plasticy) filler was modified to accept inlet from auxilliary tank/s. If you can get hold of the earlier metal type filler they can be modified as Erich has done above.
Rough drawings also attached.
If you know a good sheet metal worker he should be able to knock one or two of these up relatively cheaply.
https://www.aulro.com/afvb/images/im...16/08/1168.jpg
https://www.aulro.com/afvb/images/im...011/07/945.jpg

