Few things:
Don't mention the word mod chips. They are illegal so no one can talk about getting them or anything here in the forum.
Second, welcome to Acidmods
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Third, there should be a link to a mod done with the GH controller, but it was a huge project, I think that was done by Cyberprot.
If the program in the slim is similar to phat where they didnt really change it so that if somehow an HDD was connected, it would accept it, then some rewiring can be done to just have it there and outside the ps2, or even rewire through a usb port.