Proper spelling of variant of "suspicious"

I'm not sure if it's an Aussie thing, but if something is suspicious, then it's sus(s), e.g:

Someone added me on Facebook but they don't have a profile picture. I think they're a bit sus(s).

The problem is I don't know whether it is spelt with a double "S". Urban Dictionary has both spellings, and Dictionary.com and others just have "suss" as in "to suss something out".

Could anyone provide a reference?

Both spellings are used:

Sus, also suss:

• (noun) Suspicion of having committed a crime; suspicious behaviour; often in phr. on sus. 1936–.

(Oxford Dictionary of modern slang)

Sus or suss:

• (Britain, Australia, New Zealand, colloquial) Suspicious.

• 2001, Mo Hayder, The Treatment, 2008, Bantam, UK, page 244, ‘Yes - OK, OK. Try not to struggle, Tracey. It just makes you look even more suss.’

• 2009, Barbara Ward Smith, Dead Centre: Murder Mystery, AuthorHouse, UK, page 191,
  • I think it was Amber Johnson dressed up said Marc, but its proving it, we don′t have much to go on according to her said Jan her friend has been driving her car, yes very convenient said Marc and it′s even more suss that this friend has gone on holiday, did she ever give us the name of this mystical friend? Asked Jan.

Note also the Sus or Suss Law:

• (Britain, law) A former (1824–1981) law by which police officers were permitted to arrest anyone under suspicion of having committed a crime

(Wiktionary)