Need to limit AWS API gateway incoming request body size to less than 800 KB

Hi, I am working on a requirement wherein I have to restrict the incoming requests to Lamba function behind the AWS API Gateway to be less than 800 KB. This needs to implemented preferrably at the Gateway level and need to implement it in Terraform as Infrastructure-as-Code. I am thinking that AWS WAF SizeConstraint might be the answer but looks like it will only inspect up to 4096 bytes and also not sure how to implement a filter that rejects incoming requests greater than 800 KB body size in Terraform.

Thanks in Advance