U can use a Hellfire tank or a Ofna 125cc tank in the stock location.
Hellfire tank requires modding to properly mount, nothing drastic tho u can buy the XL optional roll cage set from hpi, they also include updated tank mounts. U have to grinded/dremeled one of the mounts down so it lines up perfectly for a super clean oem look.
The standard 160cc tank is pure garbage, way to many issues around that tank it's cheaply made and dreaded half tank lean issues are more them enough reasons for me to stay away and not use it.
Don't know if u have thought about it but u can also do a mid tank mod with a FLM servo plate and Hellfire tank.
Just some ideas for u, the simplest one will be the Ofna 125cc tank in the stock locatio, no modding what so ever but u do lose some run time...
---------- Post added at 11:03 AM ---------- Previous post was at 10:54 AM ----------
Ur best is just to get another stock tank and go from there, it's only gonna cost u another 10 bucks or so. If u continue to have issues with it then look for another tank design.