Well, in the use of cuff straps on units that require them (ones that are made for them) you DO NOT un-strap them at all once adjusted. The strap is adjust for a light snug fit around the larger area of the upper forearm, so when you kneel down to dig or otherwise you just slide your arm out, and then just slide your arm back in.
There isn't any need for a arm cuff strap on a unit that is well balanced and ultra light, the cuff rest (light upper pressure) perfect against your forearm.
Now, the older big boxer units that were out on the market needed the arm cuff strap because they were so heavy and out of balanced that the cuff wouldn't "Rest" with the forearm, you actually had to keep pressure on the cuff by tilting (applying force) at the grip or the cuff would fall away from your forearm.
My Omega comes with the cuff strap, buts its worthless to use it. Now, that's not to say you couldn't rig one up on your Tesoro, but first, try this,
Pick up the detector,
raise the coil up off the floor/ground,
do some slow swings of the coil,
does the cuff seem to "rest" against the forearm? (Tesoro are VERY slow motion detectors) if your not trying to mow grass with it then the cuff should feel cradled pretty good on your forearm.
Now, if your fresh water hunting and trying to swing the coil in the shallow water then I could see more of a need for a cuff strap.
Or, maybe swinging the coil in taller maybe wet grass you may get enough resistance of motion at the coil to cause your forearm to want to come up out of the cuff.
That's my two cents.
Happy New Year Everybody!!!
Mark