No experience with the FLM 58, but I use a Manfrotto 468MGRC2 all the time and I am greatly satisfyed with its performance! The hydrostatic lock is rock solid with a simple 1/4 turn of the knob, and the adjustable friction on the ball when the hydro lock is open can be adjusted very easily with its control knob, which has an additional click-detent feature to prevent the friction setting to be changed inadvertedly.
I use this head with a Canon EOS 20D, BG2 grip and all kind of lenses up to a 100-400L zoom, and I never experienced any slippage - often the friction lock is enough to keep the camera exactly where I point it - and there is absolutely no shift of the aimpoint when closing and opening the hydrostatic lock knob if the friction lock is properly adjusted.
The base also has an independent pano feature, with its own separate locking knob.
In my book highly recommended ad a relatively reasonable price.
Happy New Year,
Hi Stefano: Thanks for the feedback.
DarkPenguin said: "How about a kirk?"
A Kirk is on the shortlist!