Rename the title of any Aircraft.CFG file to: 

title=Custom Tundra

EXAMPLE:

[fltsim.0]
title=Custom Tundra
sim=B18
model=Main
panel=
panel=
sound=
texture=
kb_checklists=Beech18_check
kb_reference=Beech18_ref
atc_id=N2650N
atc_airline=G-AJJD
atc_flight_number=
ui_manufacturer=Flysimware
ui_type=Beech 18
ui_variation=Red 1
ui_typerole="Twin Engine Prop"
ui_createdby="Flysimware"
description=