Domain mapping plugin speed slows site down

Hi

Whenever I do a speed test of one of my customers websites at pingdom, the domain mapping plugin shows up as the longest request. The request is always in this format:
http://MyNetworkURL.com/dm-sso-endpoint/1439873893/?dm_action=domainmap-check-login-status&domain=www.MyCustomersDomain.com

The request takes 1.5 seconds out of a total of 3 secs roughly.

Can I speed this up/get rid of the check somehow?

In the mapping plugin:
Cross domain autologin is enabled.
Load Cross-domain autologin asynchronously is ticked Yes

Thanks

Ciaran