You think you have trouble with it loading the SM now? Wait a few months. After repeatedly cramming a knife in there you may find it won't load original PS2's worth a damn as well.
Seriously, your better off with a chip. Even if it's the cheesy swap mod--it's still safer than cramming something in there and forcing the drive open. The guides on the tray are very thin and chip off very easily, not to mention the rubber dampers in the corners of the drive housing. Knock those puppies loose and you can pretty much hang up verticle installs or loading unbalanced discs.
As for the SM vs. GS/AR debate--they both have issues. Sometimes you will need to do Double (or in some cases triple) swaps to get DVD backups to boot. It really isn't worth the headache and risk to go without a chip of SOME sort. There are plenty of guys who will run the install for you pretty cheap. The chips cost virtually nothing now, so there really is little excuse to not get it chipped......just think of how much it may cost you to repair or replace your PS2 when it goes FUBAR on you.
If it ain't broke don't try to fix it! But, hell if you can tweak that bastard just a little bit more....hehehe.