| I have a Thumb 5'er, and use .135's (DR Drop Down Tuning). I previously used the Low Riders too, .130, and loved em. Since I am a big fan of super-fat bass strings, and absolutely refuse to file my bridge (cannot be undone!), I use pliers to flatten the ball end of the strings.
With the .130's, I only had to flatten the B string, with the .135's, I had to flatten both the E and B, and it was a BITCH to get those suckers in there! Hurts to use pliers, I recommend a vise if you have one handy. It does work, and doesn't mess up the strings any (as far as I can tell).
If you can order a new bridge from Warwick with wider slots for a reasonable price, that would be the other way to go. Then you would have a narrow bridge AND a wide bridge to choose from. Though that may not be very cost effective.
If you do file your bridge, and I do not recommend you do, be sure to go at it in very small increments and only remove as much material as needed for the string. File in one direction, away from the ball slot, little by little. Some .135's are almost as fat as the ball at that end, so care is required so the ball still seats without slipping out.
Good luck!
__________________ Warwick Thumb 5 bo | Mesa M9 Carbine | Mesa PH210 | DR Drop Down Tuning |