Sunny hill's aluminum bottom metal requires your mag box to be cut and its two pieces bolted together. For the price they want Indont think it's a good deal given the two points mentioned above.
What’s the best option out there for lightweight 70 BM?
PT&G... the trigger guard and floor plate should be re-contoured, then you’ve got something (as long as the inlets for the actions screws are not machined too deeply). In several cases it took 6 mo’s and several returns to get one that was machined correctly.