You can't do this on an application profile, however, it may be possible with and application rule. NSX-V application rules use the same ACL syntax as HA proxy (some examples available in the Application Rule Examples section of the admin guide). You won't find anything like this in those examples, and unfortunately I don't have an easy way to test this particular scenario myself, but most front end native HAproxy conditions/actions also work in NSX-V app rules so I'd recommend starting with the HAProxy version 1.6.14 - Configuration Manual and playing with matching the req.hdr_len condition to block anything greater than your desired header length.
