I will stick to my guns and say that an undersized cart is probably the worst nightmare....I use the intex pools as a prime example!
Evan, you misunderstood me, I think. An undersized cart WILL be a nightmare, but so will an undersized sand or DE filter.
Cart: Torn filter, crap blowing into the pool
Sand: Broken lateral, sand AND crap blowing into the pool.
DE: broken/torn screens or fingers AND DE and crap blowing into the pool.

In all three you need to replace them with a proper sized filter and then you have to clean out the pool..

I started with an Intex with a little 1/6hp cart. Hated the thing (the pump that is--loved the pool)--just like Evan did. Not because it didn't do the job--it did, with care, but because cleaning the d*** thing was a messy pain. Luckily, I bought a case of filters for about $10 each and I'd make each one last 2 weeks, cleaning it once then chucking it. It didn't keep us from enjoying the pool, just it was one more pain in the patoot.

If your sand filter is properly sized and you have properly backwashed it all season, the dirt and sand will not be a problem. Late in the season you want to make sure your water is super-clean before closing. Then my final water treatment is to push that clean water to shock level and close--my filter is clean, my sand is FINE.

Check with Poconos and see if he's followed your procedure. Bet he hasn't.

That IS what's great about this forum...We CAN be candid in our opinions. Evan and I can disagree and STILL have great respect for each other.