SSL Forward Proxy, iRules and Client Hello

Hi all, I am seeing odd behaviour using SSL fwd proxy (SSLO):

My intention is to use the client hello (SNI) to influence SSSL profile selection. I have 2 SSSL profiles setup, let call them A and B

For trusted connections (i.e. certs issuers in SSSL CA bundle) is am unable to extract the SNI from the initial CH, using the CLIENTSSL_CLIENTHELLO event and [SSL::extensions -type 0]. These are send to profile A based on SNI.

I have pcaps showing the CH incoming to the F5. I assume this may have something to do with the 'verified handshake' functionality. It appears the test client browser keeps attempting connection and I see inconsistent results (some connections are reset, some succeed). In irule logs its apparent the SNI does eventually become available in the CLIENTSSL_CLIENTHELLO event.

For untrusted/self signed etc this doesn't appear to happen, these are sent to Profile B (identical to A for testing purposes) so my assumption is the F5 is doing some kind of SNI processing (compare to CN's in trust store?) and then connecting to the server for 'verified handshake' before releasing the SNI into the CLIENTSSL_CLIENTHELLO event?

I have seen an iRule that effectively disables SSL then parses the raw client hello for SNI, I expect this may work as it would intercept the raw CH so the F5 cannot interfere or do any server-side preamble, but I'd rather do this within the realms of defined events if possible... :-)

Any suggestions or comments welcome! thanks