My theory on shredding is...
1, Overloading to the point of getting the tub so jammed packed none of the clothes ever move, they end up getting moist, the agitator shreds, and that's it.
2, Wrong size Water Level. I had to use a Shredmore for 2 years and Underloading with Extra High water levels and Slow Agitation seemed to relieve the shredding.
3, Mechanically... I feel the stroke is too aggressive. Never likes the machine for that reason. Shredmores always reminded me of some Meth Head. Just chattering away and making no sense with generally hardly any accomplishment but being annoying. Kind of like a Circuit Queen. Pretty to look at, Nice features, but lacking or poor performance. (Sometimes) : )
I don't think your Disc under the agitator will make any difference at all.
Once a Shredmore, always a Shredmore.
But I will say this... Man !!! they last and last and are pretty much indestructible. I have a woman friend that for 15+ years overloads the crap out of that machine and it stil chugs along. I have moved her clothes to the dryer for her and what she packs in that machine, you could fill a 35 lb Milnor. And the machine has NEVER snapped the drive coupler. AMAZING.
How are the results of overloading like that ? They wear things once, have really no soil level, and I don't think they notice. Does the Fabric show signs of wear ???... As they say on Rowan and Martin's Laugh in... "You bet your Sweet Bippy" they show wear.
And Shredmore Believers, Owners, and Advocates... This is a personal opinion and my thoughts. Your mileage may vary.