Yes, converting a Tapco G2 set to a two-stage is easy but requires patience and incremental removal of the underside leading edge of the disconnector...very gradually (this is where Tapco's axis sleeve really pays for itself since you have to repeatedly remove and install the FCG until you get it the way you want it). You gradually reduce (using a file; nothing as drastic as a Dremel) the thickness of the lower leading edge until the top of the connector (the hooked part or "business end") of the disconnector just barely touches the back of the hammer before the hammer is released. Since no AK alignment is exactly the same, this may take a very little or a considerable amount of filing before the two parts touch. I have done this on 8-10 kits and find that it normally takes as many as ten tries to get it the way I want. Taking too little material is better than taking too much. Regarding "safe", think about it: as you remove material and cause the disconnector to "lean forward" you're actually causing it to engage the recoiling/recycling hammer sooner rather than later, so you don't increase the risk of it inadvertently going full auto. The only problem I've have ever encountered (in only one case....remember, specs very slightly from AK to AK) is that I had to file/remove so much material before the hooked part of the disconnector touched the back of the hammer that the compression on the disconnector spring was weakened too much and i did experience a few doubles when test firing. In this one case, the remedy was easy in that I inserted a very small ball bearing in the base of the hole that holds that spring, thereby artificially lengthening the spring again: problem solved (a short length of nail of the correct diameter could also be fabricated.)
My results have been universally successful (including that one "ball bearing" episode); however, I must admit that the degree of pressure required for that 2nd stage release does vary from case to case, ranging from light to very light. I'm so pleased with this process that I've done it to all my AKs in the "shooter" category. It has really improved my long-distance accuracy.