I've got Hagerty too, and they have a great product. I've got the same restrictions, but the pricing is very fair and I love the single liability charge foe the whole fleet.....I pay 437.00 annually for 4 cars.
However, for many years I had my cars insured through the same major insurer I had my daily drivers with (and where I work) They had a specialty product for old cars called "stated value" which turned out gave them the option of paying the LESSER of actual cash value (ACV) or stated value. I paid extra to give them the option of paying me less! Hell, I work there, you think I would have known better!
I dropped that endorsement, but kept the policy as it was payroll deducted and just easier. I insured the old cars just like my drivers, with collision and comp. And we have alot of insured's who do the same, and we settle the losses fairly based on current market value.
But when I finally did the math, I was paying better than 2000.00 a year for all 4 cars, my company just couldnt match the specialty pricing of Hagerty. Plus, we dont offer an agreed pricing endorsement like Hagerty where if the car is totalled, they just pay the value placed on the car when they wrote the policy. However, this can bite you if the value of your car (ACV) goes up and you dont adjust your coverage accordingly. And they wont call you to tell you you're under insured
Short version
Specialty carriers are much cheaper, but often come with restrictions
Stated Vaue BAD, Agreed value GOOD
If you have Agreed value coverage, watch the market and adjust
Always spring for Comprehensive and Collision coverage - it's fairly cheap and even if a loss is the other guys fault, their company might be (and often are) jerks who have no idea what they're looking at....