Mike, I only have dollies for attachments I can't use the with the iMatch. The tiller is so small that I can only use it with my 21 HP Kubota
B21 TLB. The post hole digger (PHD) can't be used with the iMatch, so it's on a dolly. And when I use the PHD I have to take off the iMatch, so it has a dolly.
My other bucket for the backhoe weights a lot, so putting it on a dolly helps when I change out to that and helps store it. My front blade and blower for the JD 318 garden tractor are on funny looking low deck dollies so they can be put on with relative ease.
But the box blade, MX6 rotary cutter, sickle bar, and land plane are iMacth and have no dollies- I have to put them where I want them. You can see in the PHD picture the MX6 and sickle bar in the background. Part of what makes the iMatch work is having the attachment on the ground so you can push against it. It would be harder to put an attachment on with the iMatch if it was on a dolly than if it was on the ground. The top and tilt on the 3 point hitch also makes backing into the attachment and hooking it easy. Yes, you could lock the casters but I think you'd be stressing the casters and dolly every time you hooked up.
It's a good mix- enough stuff can move around that it can be stored efficiently. I've got one dolly left to make- I've got a 6' landscape rake that can only be used with the
B21, so it needs to be on a dolly to make it easier to attach. Also, the older I get the more I like dollies and my iMatch

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Pete