In cross account connection how to configure "RDS Proxy Endpoint" for Postgres RDS Aurora using Babelfish ?

MSSQL RDS is migrated to Postgres RDS Aurora using Babelfish. This migrated db works fine with direct endpoint of RDs Aurora Instance. But fails to recognize Old MSSQL queries , Stored procedures when "RDS Proxy Endpoint" is used in cross AWS account connection. Following blog 1 https://aws.amazon.com/blogs/database/use-amazon-rds-proxy-to-provide-access-to-rds-databases-across-aws-accounts/ 1] Any possible workaround ? it is one more limitation of RDS Proxy?

2] Also, security group configuration / rules for "RDS Proxy Endpoint" are not clearly mentioned in the blog 2 https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/rds-proxy-endpoints.html