The suds is because of the spin.

Even the lowest foaming of detergents will produce this spin suds.

All detergents here in Europe (where they are all low foam) do that too especially in spin drain machines vs neutral drain ones.

I had this problem. 

As it increase the speed it whips the suds and if you have a tall elbow siphon and the drain hose is not sealed will back up as it is unable to go past the siphon unlike plain water.

Sadly the oil effect will vanish a lot as soon as first water pass through,  but the problem is in the last water drained as the spin speed kicks in stronger.

Try to seal the drain hose where it enters the stand pipe with a fine rubber ring or rubber gasket to have the hose pressed sealed tight into the stand pipe.

No suds will go out.

This is not a matter of detergent, some loads also tend to produce more spin suds than other.

Heavy towels for istance.

For example these might work, may be smaller than the SQ adapter?

www.amazon.com/Silicone-Washing-M...

The size of the ring really depends on the size of your standpipe, so as you say that the adapter that came with the machine is too big for your pipe you need to chose something thinner that would fit and create a gasket.

The gasket on Amazon that i have posted looks more thin than the Speed Queen adapter, anyway there are measures on one of the photos.

The siphon I am talking about probably is under the floor and or before entering the main drain line. 

Siphons are there to avoid stench and or gases from the drain line or septic tank to come up the pipe.

Especially in a standpipe for a washer.

If the elbow of the siphon is tall or S shaped suds will Just not pass but tend to accumulate inside the pipe before the siphon and come out from where the hose enters without being sealed with a gasket.

For siphon i mean a trap.

They have the same kinds of gaskets elsewhere for way less.

Anyway you may find Universal gaskets you can cut even in hardware or plumbing stores.