A company operates application servers on Amazon EC2 instances deployed in separate VPCs interconnected via a transit gateway. The EC2 instances are launched in private subnets with routes to the transit gateway for both internal and external connectivity. External connectivity is facilitated by a VPC equipped with firewall devices that inspect packets entering and exiting through an internet gateway.

To assist the application team in increasing the payload size per packet delivery between the EC2 instances, while ensuring all network traffic continues to route through the transit gateway, what steps should the network engineer take?