My update about my radish and peas during a very cold period in March which I knew was coming. In short, insulation works. See details in the rest of this post.
First my radish. I covered them with 34 grams of fleece. They did well. No loss. But some of the more tender cotyledon leaves did show frost burn with white blotches (The larger plants in the photos are over wintered turnips; I planted my radish between them as a follow-up crop).
Second my peas. Peas do not like cold temps, so I kept them under both a low tunnel and fleece (34g). They came through just fine. No damage. Maybe a little bit bent over from the fleece, but they will easily recover from that.