stem-steer tube ?

yes. (well maybe, depends on who you talk to...)

some, if not all, full carbon fork maunufacturers recommend having a spacer above the stem (steerer tube sticking out above the stem) so that the stem does not clamp around the top of the steerer tube. clamping the top of the steerer could deform or crack it. I see some, but not many installed this way. it looks peculiar, so I'm sure some folks don't do it for that reason. afterall, appearance is everything!?!?

I'd agree with RV, this is the way to fit a fork with carbon steerer. This is the the method favoured by LOOK and Time.

8mm is a bit too much unsupported carbon. The top pinch bolt will be sitting over the rim of the steerer. Too much torque could start a crack in the carbon. Best way to fix this is to get a bung with a long sleeve at the top i.e, the FSA model, probably the best design around for tackling this particular issue.

As an addition to my original post I would mention that this fork, a Serotta F2 made by Reynolds, has a metal insert glued into the top which incorporates the star nut. Therefore there is no unsupported carbon at the tubes termination. I have removed the 3mm spacer which results in now a 5mm difference from stem top to steer tube. Safer but is it safe enough?

Henry

The bonded metal insert may get you out of jail in this instance. Main thing to check is that the top bolt is sitting below the rim of the steerer. Measure both distances with a vernier or a small rule. If the top bolt is sitting above the rim of the steerer, it could lead to ovalisation or cracking of the steerer plus uneven torque on the stem bolts, not really situations you'd want to occur.

good luck

Neil