Have seen this done all different ways.....
The way we would do it, and advise , for warranty reasons, would depend on whether you have a self Draining system ( eg the bottom bead is sat up on plastic shims to allow water out ) .
If you have a self draining system then we would advise just Glazing Tape , to both sides of the sealed unit, doesn't matter if it sits proud of the bead ( into the visible glass area ) as you can cut this excerss off with a sStanley knife.
A non ' self draining ' system , we would advise , again the glazing tape, but also Low Modulus , neutral cure silicone ( usually clear), which would be applied to the gap betwen the edge of the sealed unit , and the edge of the frame. Basically put the sealed unit in using glazing tape , then before applying the second layer of tape ( for the beads ), fill any visible gap within the rebate with the silicone, this prevents any moisture getting to the actual ' seal ' of the unit. I know some will say that surely that is what the tape is for , but wood moves a lot in varying weather conditions....
As goes materials, any decent silicone, ( must be Low Modulus , Neutral cure though ).Brands such as Soudal or Silfix should be fine, but from experience we tend to find the Butyl Flexistrip, that Hodgsons sealants manufacture to be the best ' tape ' for wooden windows, this comes in White , MAhogany and Black ...If you can't find it , I am sure we could sell you some!
