Spreading prim limits between lots

I'm considering getting an island, and setting up a series of lots separated by a network of protected street lots. That way, people can build within their space without overflowing into the street.

Problem is, that means the streets are eating up SQM and thus prims that could be going to the homes. Let's say we have two houses that are 1024's and a 512 street between them -- that's 234, 117, and 234 prims. Ideally, I want to say "Two 1024 lots, 292 prims each!" to spread the road's allocation over rather than having it go to waste.

The only way to do this I know of is to have both homes and the road all owned by the same group -- that way they all share the same prim total. I could even turn "group build off" on the road section. But that also means the renters in Lot 1 can dump prims all over Lot 2 if they feel like it, etc.

Any suggestions for how best to approach this puzzle? Thanks!

The sim i am in consists of 4096 plots, separated by a grid of water canals. The property lines simply extend into the canals. The buldable surface area of your lost is actually less than 4096, but you do own the entire 4096, and its prims. We have a covenant that says you cannot put anything into the canal portion of your property (including ban line) that in any way obstruct the navaibability of the canals. I'm in Kush. You can contact our estate manager Rockwell Ginsberg if you want to ask him about it. For the most part, it is working out fairly well for us.

You can change the prim factors on each lot to give prims to the 1024's and to take prims away from the 512's. Your normal lots would have a prim factor of around 1.25 and you can lower the prim factor on the 512's to just enough to allow you to build the road.