Tectonic™ Fold-Up Cover
Yes, the Tectonic cover would work with fuel tanks, as it does not drop down into the bed for operation.
Landmark™ Retractable Cover
Unfortunately fuel tanks are not compatible with the Landmark cover. This cover retracts into the bed as demonstrated below:
Accessories placed next to the cab use the space our cover needs to operate. It is not possible to modify or customize our cover to work with these items.