My current setup and what has worked best so far is:
1. Wingnuts replacing the thumbscrews and some washers to reduce friction (M3x0.50 wing nuts and M3 washers). This makes adjustment pain free, especially when the bed is hot)
2. Metal arm stiffeners (there are several kinds out there, mine don't seem to be available anymore, but I got mine on ebay)
3. Thick glass plate (1/4", Mcmaster part 8476K74, or I believe the Flashforge glass is the same)
4. Give the bed a thorough heat soak at the intended bed temperature before leveling