I have a PS2 slimline v12 that I purchased a modded fliptop for so that I could use SwapMagic without using the little metal keys (they kept moving around too much and were a pain). I had no problems getting the PS2 apart, installing the new top and getting it back together.
The problem comes in when I try to turn it ON, now. The reset button is lit up red but when I push it, nothing happens. I'm not sure if the reset button isn't lining up with the piece inside or what. :/ The rubber(? hard plastic, whatever) piece on the reset chip keeps coming out (not the plastic part. just the little nub) when I have it open, but I'm able to get it in there and keep it in there when I get the top on, so I don't think that's the problem. The cable looks just fine; no holes or tears or creases anywhere.