If I am understanding you correctly....
I do not think there is enough room to double up the bury inside the line. Not to mention you will seriously deform the line and as DemostiX, cause a serious stress riser.
Also, substantially shortening the whoopie seems excessive. With 7/64 using a locked brummel, the bury length is just over 4.5". IMO thats not very long. You are only talking about shortening the total length by 2.25".
Second also.... By increasing the diameter for the fixed eye bury and then starting the adjustable eye bury close to the end of the fixed eye bury, you will have some serious deformation of the line at this junction.
Please proceed carefully.
DemostiX, Dynex is not Amsteel Blue. Please use caution suggesting different splice methods for different types of line. Unless you have personally tested this splice in Amsteel Blue......