I cannot believe how good my spider I 50w combo sounds now after i made some modifications on it,i first made my own version of a weber beam blocker,i cut a 3.5" circle out of tablet cardboard,you can use other types of cardboard as long as it is the flexible type (not the kind from a cardboard brown box because it does not flex well and may be too thick),i then glued two black emery boards(3/4"x about 7" long to the 3.5" cardboard cutout),i cut about 1/2" off the end of each emery board so that the ends are square only on glued side of the emery boards that attach to the 3.5" cardboard.
I used wood glue to attach the emery boards to the 3.5" cardboard,on the other side of the cardboard cutout i cut a piece of black felt to a 3.5" diameter and used stick glue to attach it to the cardboard(do not use elmers or wood glue because it may soak through the felt),the felt side faces the speaker grill cloth,i used the felt because it will stop any vibration or resonance from the speaker grill cloth.
I put two small pieces of duct tape on the outer rounded ends of the emery boards so that it will hold the beam blocker better under the front inside of the grill cloth.
The beam blocker filtered out a lot of high end harshness that i got on the metal setting and will also help the insane model sound better but i like the metal model better and it just sounds great now! The other amp models sound better also,i get a good overdrive blues tone from the crunch amp model without the harshness it had before.
I also added a backboard to my spider,i used 3/4" thick particle board, just measure the width of the rear of your amp and leave about a 2.5" space from to top rear of the amp to vent it and have room to plug in the power cord. I added two 3/4"x 10" strips of pine wood to the sides on the amp to hold the backboard in place,use three wood screws per strip no longer then 1/1/4" long and also grind down the tips of the screws so you do not go through the sides of the amp. Drill three holes at equal distance on each side of the backboard,use 1.5" black wood screws to attach the backboard to the pine wood strips. Note: before you attach the backboard paint it with flat black spray paint and also paint the tops of the wood strips or you can paint the whole length of the strips,i also used grey weather stripping on the wood strips and on the bottom edge of the backboard to reduce and or stop any vibrations.
My spider sounds better with the backboard in place,it has a better low end now and rounder tone.
Sorry for the long post but i just wanted to share the improvement i made to my spider I.