Well...this past Saturday on the 29th I tried another intro.
It went a little better. I managed to keep them together for about 1 1/2 hours before they wanted to hurt each other. I really thought it might work today. The split tank was cleaned out. It had to be cleaned. A tiny bug problem. There are wheels on both sides of the 20 gallon split now.
They seem to want to be together. They sleep in each others beds. They like the scent of the other gerbil but when face to face. Nope. They are both dominant type gerbils. One of their fights, I got bit hard with the gloves on from Bud. I think Bud got bit in the rump. No blood but it is tender to the touch.
The neutral territory seems to work for the short term. What do think? If anything, the split can be permanent so at least they won't be totally alone. I will still do the flip flopping and the butt sniffing.
Will keep on trying every weekend. I have never had failure of putting two gerbils together.