Clek stated on Facebook today that you can use both the rigid LATCH and seatbelt together when forward facing over the stated LATCH limits:
"The new requirements for LATCH does not pose a safety threat for seats --it is a way to give all car manufacturers the same limit. You should check your vehicle's owner's manual to see what their limits are if they provide one. And yes, once your child reaches the upper limits you can use the vehicle's seat belt AND because our rigid LATCH has an independent system that is not connected to the vehicle seat belt system you can use both the rigid LATCH system with the vehicle seat belt together. I hope this is clear, if not please call our customer service department at 1-866-656-2462."
"The new requirements for LATCH does not pose a safety threat for seats --it is a way to give all car manufacturers the same limit. You should check your vehicle's owner's manual to see what their limits are if they provide one. And yes, once your child reaches the upper limits you can use the vehicle's seat belt AND because our rigid LATCH has an independent system that is not connected to the vehicle seat belt system you can use both the rigid LATCH system with the vehicle seat belt together. I hope this is clear, if not please call our customer service department at 1-866-656-2462."