Well, sorry for me not reading carefully - you want to put it on the doublet directly - so yes, you will need some choking. Look here -?
This guy did it properly for the SG239, it is the same for the ATU-100.?
And this is how I choked mine -?
The GDT's protect the ATU from overvoltage and the resistors leak the static to ground, the GDT's are 1.2kV littlefuse types.
The main link for the BALUN's and chokes is DG0SA -?https://www.dg0sa.de/inhaltbalun.htm
Billian Marinov