Farmers 'sow' seed potatoes at a given weight per acre. So if the seeds are smaller, they just plant them closer along the row, but the yield weight, over all, would still be as expected. You will need to adjust your planting spacing in the same way.
I recently forked over last year's potato bed and found all the small spuds that I missed last year, and they were all growing strongly LOL
I wouldn't like to plant them under a huge ridge, as I don't know if they'd have enough nutrients to get them through to the surface. I only earth up as they grow through and if a frost is forecast.