Here is exactly what I do with the OS LA .15 on a pressure bladder.

The George Cleveland bladder material puts out too much pressure for me so I used tubing from McMaster Carr

The Materials

The bladder

Catalog Page 97, Natural Rubber Tubing, Part number 5234K44, 1/4" ID with 15psi pressure rating, .66 per foot in 15' and 25' lengths. I cut mine to 3-1/4" for SSC. This holds 3-1/2 of fuel and is nowhere near filled.

The tubing from bladder to engine

Catalog page 97, Part number 5234K93, 1/16" ID, 25psi, .59 per foot in 15' and 25' lengths.

Fittings for the bladder

Catalog page 111 - Barbed Tube Fitting, Tube to Tube fittings (nylon). This is used in the thin fuel tubing from the bladder to the engine. I use it at the point where I open the line to fuel and defuel. 1/8", Part Number 5463K333, $3.81 for package of 10.

End Plug for rear of the bladder

Catalog Page 112, Barbed Tube Fittings, Plugs - 1/4" Part Number 5116K112 $2.02 for package of 10. Use a small tie wrap (larger ones leak) to hold this in the tubing. It has a barb on it that the tie wrap will cinch up to and it can be over and over.

Reducing Coupling to connect bladder to the line to fuel tank. Catalog page 111, Reducing Coupling, 1/4" to 1/8" Catalog Part Number 5463K629, $5.81 for package of 10. The 1/8" barbed end fits well in the 1/16" ID tubing. Attach to the 1/4" tubing with small tie wrap.

Now - how to use it:

1. There is no need for a reducer in the fuel lines.
2. There is no need for a fuel shutoff, your carb will kill the engine
3. Fill bladder [1] with two two ounce syringes. One filled to the max, the other to 1-1/2 ounces. The end fitting on the syringe is the single most important accessory. It has to go into the 1/16" tubing without slipping off when you fuel.
4. Connect the fuel tubing to the engine spray bar by running it to the fitting that normally goes to the carburetor. This is backwards, but it holds pressure better.
5. Set needle valve to 3/4 turns open, this is probably a rich setting.
6. Prime, start and enjoy 7 minutes of rock solid run time.

Make sure your bladder and your fuel lines are not kinked or distorted. You will have inconsistent runs if they are. Just before the bladder is completely empty the engine will richen up slightly. You have about 20 seconds of run time from this point till it quits.

[1] Note: When you fill a bladder for the first time, you need to train it. You will want to have the end near the plug fill first with fuel. So, what you do is attach a fully extended syringe to the bladder (you don't need to fill it with fuel, air is sufficient). Then, hold the bladder with your fingers wrapped around all but the last inch near the plug. Next, Push the plunger in, while preventing the section you are holding from expanding before the last inch inflates. Once this last inch inflates the first time, the bladder will always inflate first from this point.