What I did for my O.S. .91 wasw to mount a spare servo arm to act as a bellcrank. This allwed me to choose which holes the servo output and the final link rods connected to, giving a linkage which provides full throttle range with normal servo travel. (no end point adjusting)

In my case, I drilled and tapped the side of the engine bearer and used a small piece of brass tube as a pivot bushing. I used a straight across dual arm and the holes that worked best turned out to be furthest out for final output, and middle of 3 for the servo's pushrod. I used a ball-link on each end of the final link rod, which gave plenty of room for adjusting the linkage.

You can do that... or try shifting to a flexible cable type throttle system. Insert the last 8 inches of the cable sheath in the correct size copper or aluminum tube (not brass!) and bend the tube around a convenient object for the U shape. Solder harden the portion of the cable which will not be inside supported sheathing.

You don't need a lot of force on throttle linkages... so the finer cable used in 1/2 A aircraft is appropriate. It will make tighter bends. The OD of the sheath is about the OD of the normal throttle cable. (how to save a few grams in one easy lesson... )

You could also try mounting a sub-micro servo up near the engine and using a VERY short linkage. Again... low force needed, so the light duty servo shouldn't be a problem.

A light spring to close the throttle and a dacron thread to open it will work... Ball point pen springs give plenty of tension. If set up correctly, a failure of the reciever system will allow the throttle to close. (The RX sending no signal to the servo... it will drift with little force applied.)

Don't get stuck thinking of how to use a "conventional" linkage setup. There's lots of ways to make a throttle system work.