You will probably need a weed fin typically raked at about 45',
which translates in size (with 45' rake) to around 36cm for 8m and 32cm for 6.7m.
Brand of weedfins depends on what is available at your location (varies..)
Some known good brands in weedfins include Tangent Reaper and Lessacher.
The handling/control/speed of these heavily raked fins is not so bad
an overall compromise as you might expect
Cheers ~ Ian