Julian,
Congratulations on passing your IRT.
YNSL
Half scale deflection is half of whatever you happen to have on your instrument, be it ADI, HSI or whatever - and no, most HSIs I have flown don't have only 2 dots. Just as a matter of interest, should you elect to use a FD for your IRR (if you have one of course) you will be assessed to half the normal limits!
