The iZi Flex FIX i-Size is approved in UN R129-02 without any additional SIP+ or SIP bumpers (at the inside of the vehicle). The SIP bumpers and the SIP+ improve the side impact performance and should always be used at the door side of the vehicle. Only when a third CRS is used in the middle position of the vehicle, may the SIP bumper be taken off, but only at the inside of the vehicle and not at the doorside.
The possibility to install three iZi Flex FIX i-Size seats in a row depends mainly on the car, and where the ISOfix anchorages are mounted in the seat of the car. If possible, use ISOfix for all three of the seats; this is normally only feasible in a vehicle with three seperate vehicle seats in the second row. If there is less space, or if there are only two ISOfix anchorages placed a bit out of line, you can use the BeSafe iZi Flex i-Size seats in combination with the vehicle belts only.