Has anybody ever installed 2G pistons in a 1G engine?

This has been done on occasion. 2G turbo pistons are a higher compression ratio (8.5:1 instead of 7.8:1) and are capable of delivering more power, with a higher probability of detonation. The same should be true of 1G NT pistons (9.0:1), but the NT pistons are not designed to withstand the stresses inherent in turbocharging, making the 2G turbo pistons the next best choice.

In most cases, the 1G connecting rods must be machined in order to fit the 2G pistons.

As a side note, Mitsubishi sells factory overbore pistons in sizes 0.5mm and 1.0mm larger than stock.