Descent II via DosBOX 0.74 supports 2 controllers. (combined TM Warthog as one controller)
However my "2nd" controller is the Simped-F16/USB and according to JoyToKey (Ver3.7.4 still latest see link below) the "rudder" axis is seen as Axis6 and therefore is not seen by the game. This was only found through trial-and-error only after switching to "other" tab and checking "Use Axes other than X and Y" the I have not looked any deeper than to discover Axis6 instead of the 4th DOS Axis. ie: DosBOX can see 4 axis only. The Warthog combo uses 3 axis (stick's X&Y and Thr's Y) leaving the 4th for something else. BTW, In TARGET, I disabled all axis except these including disabling the left thr.
So, I'm using JoyToKey.exe (as suggested (in general not to solve Descent's issue) from DosBOX's web site) to map the left and right bracket keys to be bank left and bank right respectively and set these keys as same in Decent II's keyboard settings. Works but not subtle at all. Always banking too much too fast. Using the CPU settings to slow it down is not the right way cause it causes the graphics to be choppy as in too many frames being skipped. http://www.electracode.com/4/joy2key/JoyToKey%20English%20Version.htm
As per my testing: SimPED-F16/USB X=Right Brake; Y=Left Brake; Axis6=rudder