Dynomax welded vs X

You want the center of the "X" 8-12 inches behind the end of the tailshaft. Mine is centered exactly 10" back. To close to the mufflers and it will cause a decrease in flow due to loss of momentum of the air/gases

Oh and i have the ultraflow welded 2 1/2". Quieter idle than my flowmasters (i had super 40's) but louder when in the trottle. Welded is considered a race muffler though.