In my new HT (Chumba HX2) the cable routing for the gears is along the down tube & under the BB shell.

The frame has cable bosses on the head tube and then runs just inners to one of those BB cable guide thingies.

Routing the cables so the RH/rear shifter cable goes down the LH side of the HT & vice-a-versa the cable inners cross about 3/4 of the way along the down tube.

my question is will this cause any problems with wear?

Alternatively would I be better to route the RH/rear shifter cable down the RH of the head tube to prevent crossing? Although this does leave a very short section of outer from the shifter to the boss on the head tube.

I’ve always crossed them, it causes no problems.

leave it, possibly the best cable routing there is.

As long as the cables aren’t rubbing on the down tube you’ll be fine.

I normally route my shifter cables down the same side, but crossing works as long as the stops at the front are low enough.

I cross mine because it reduces the curve on the outer cable, which is a good thing. As above, it does rely on your cable stops being in the right position.

The stops are about 25mm above the bottom of the head tube and in line with the angle of the down tube.

I think I’ll leave it to reduce the curve as mentioned above