Well since the guy at the LBS suggested it i assume they have used that technique.
As far as both frames go they are AL and the headset was tight as before when finished. I wouldn't do it my Carbon Trek 6.9 since all the bearings (BB and headset) are integrated "slip fit" so the only tools I need are my fingers. Which I think is the best method.
And your point is what exactly??? Simply because you happen to have an integrated headset in your carbon fiber frame you think that justifies your procedure for a press fit headset installation??? Integrated means the cups are built into the frame so people like you don`t have the option of installing them yourself!! The only thing you`re installing are the bearing races.
And I`m not interested in what some moron at your local bike shop told you because if thats what he told you that certainly qualifies him as a moron. Suggest you have a look at the Park Tool procedure for press fit headset installation. It also lists the dimensions for acceptable / unacceptable press fit installations. The use of a vernier is recommended. On the other hand, you yourself might consider a ruler is accurate enough for your oun work methods.
Hate to buy a used bike from someone like you.