Is anyone margin lending their portfolio on the NZX50 (FNZ) ETF or similar ETFs?

Would love to see a comparison of returns over a multi year timeframe on 20-30% borrowings vs no borrowing.

ASB is lending up to 60% so taking into account a 50% drop in share prices, one could borrow $30 for every $100 invested and still avoid a margin call if the markets were to drop 50%