What should the tension be set on for quilting. the bottom thread bunches on the back of the material and I can't figure out how to resolve.

SOURCE: Thread is bunching up unside of the material does not catch bobbin thread

This sounds like the tension is not set properly for what you are sewing.

SOURCE: Tension Problem while free motion quilting

Usually dirt in the tension plates. Pull a short piece of heavy thread through them holding the thread tight between both hands, work it back and forth to clear out lint.

SOURCE: Husqvarna bobbin thread jamming

Make sure the bobbin thread "clicks" into the tension slot. However, thread nests underneath are usually caused by the top thread, not the bobbin. Make sure your thread is seating itself in the top tension disks. To do this, put the spool on the machine, pull off about 12 or 15 inches of thread, then hold this thread down with one finger on your right hand as you take the thread tail through the threading path with your left hand. When you get to the needle, tug the thread (still holding it down up top) to be sure it seats in the tensions disks. You must also have the presser foot UP while you do this to ensure that the tension disks are open. Watch the first thread guide after the spool as you sew to make sure the thread is not jumping out of there (a common problem with Des1 machines, fixed with SEs - no comfort to you and me!). I have put a small piece of tape across there with the end turned back on itself so no sticky bit is going to catch on the thread.

SOURCE: Singer Featherweight tension assembly

Putting this back together is a thirty second job if you have done it a hundred times. If you have never done it but have mechanical aptitude, it may be a challenge.

Whatever you do, don't bend the check spring out of shape!

Below is a link to the Singer site with the schematic for reassembly. When placing the check spring back in place, place it in about the 6 o'clock position with no tension so that it has a fair amount of check before pulling it up in place..

When setting the tension, at a setting of "1" the tension disks should just be slightly compressing the beehive spring. "0" is almost no tension at all. Normal sewing is 5.

Get all of the parts together and push in the cup with the numbers while screwing on the knurled nut taking care to get the pin in one of the holes.

http://www.parts.singerco.com/CPpartCharts/2_2999/221-1_221K1_221K4_221K5.pdf

SOURCE: Pfaff Select 4.0 has looping on bottom of fabric, free motion qui

Make sure your are lowering the pressure foot first before you start sewing. With the free motion foot, you still have to lower the pressure foot, this allows tension to be put on the top thread and allows the foot to work properly (when the needle goes down so should the foot and when the needle comes up it should lift the foot up.)

Also make sure your tensions are in a middle setting and that you are threading the machine with the pressure foot up.

The way to insure you will not get your problem is with the foot up, you should be able to pull the thread easily right before the eye of the needle and when you put the foot down you should then feel a fair bit of tension on the top thread.

hope that helps :)
chris