What goes today for an overcall over 1NT would have been off-limits 20 years ago
However, the theory of assumed fit does promises that you have 2 chances in 3 to find a fit when you bid with two 4-card suits, and it is a clear incentive not to be shy. Which is really proven by facts: you may have to pay the occasional 500 or 800, but, on average, you gain. Kindly note that this applies to both MP and IMP (and I would assume to BAM too).
I am a big supporter of DONT to overcall 1NT. It is simple and quite effective (IMHO the most effective overcall system). The advancer has just one rule: be always a pessimist, and don't {DONT

} change suit unless you're doubled
and you have reasonable chances to find a better fit; a less-known corollary to Murphy's law states that if you hold a 9 cards 2-suiter, pard will have no fit

.
The theory of assumed fit should be used as a general pre-emptive tool: I am not sure how ACBL rules are; OTOH, Australia is quite a free country, and EBU has relaxed a number of the most stupid rules. My recommendation is to go for the maximum that you're allowed in pre-empting at the 2-level. I play 2
♦ multi, 2
♥ weak with 4/4 in the majors, 2
♠ Dutch style. I am even thinking to ditch 2
♣ GF to play 2
♣ as a weak 3-suiter (or 5-4-3-1) with clubs as anchor suit.
Which anticipates the last suggestion: it is better (much, much better) when pard can pass your bid

Which is another reason for liking DONT.