QuiQue's Aircraft Yak-54S Assembly Manual page 34

Figure 52
Then using Velcro, strap the tank to
the plate that tank is located on.
Figure 53
Figure 54
Step 3
In both cases you need to trim the
top former so you can fit the tank,
like shown in Figure 49.
Important: Make sure the tank is
firmly secured. Keep in mind that
with a full fuel tank, say 20 ounces,
with an airplane pulling 10 G's
creates a force of 200 ounces or
12.5 pounds. With this much force
the full fuel tank might just like to
take on a mind of its own. Ten G's
would not be uncommon in some
violent 3-D maneuvers, which this
Yak-54 is capable of doing certainly
with the control surface throws that
you have available.
Also make sure use zip ties around
the tank cap and fuel lines.
34