I use a V700 with the standard holders. This was shot on a Rolleiflex 2.8C, I regard it to be great for the money. I paid about £190 for the scanner and it came with some cool AN glass 5x4 holders. I think a big thing for flatbed quality is making sure the negative is in the fixed focus region. I think I got lucky as it's close enough, but some people get
betterscanning.com holders with adjustable heights.