cantilever brake for mini bike, is the long brake line safe?

I'm hoping to upgrade the mini-bike with road bar and road brake lever. So I need to change the v-brake to cantilever brake. Since there is no housing stops on the frame for either front or rear cantilevers, I need to setup the add-on stops above the headtube and on the seatpost clamp. My question is: since the wheels are so small (20 inch), there will be a pretty long line between and housing stop to the brake. Is that setup safe?

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I suggest Mini V-Brakes with STI or Road Brake Levers.
All the compatibility is there.

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Cheers,
George.