Nevertheless, in order to make this possible - to file without the holder or to cut (which would impair its stability in my eyes) - you have the telescopic arm to the hand strap of the reflector on the one hand and on the opposite gap that is allowed in accordance with the zipper on the other hand fasten.
But it works only if you take the loose / movable retaining clip of the telescopic rod down. Namely, you can both terminals start obliquely and by engagement of the two telescopic rod back through the loose clamp and extend through fix.
The result then holds bombproof.
By the way, almost all reflector holders have installed the exact same retention clips. Consequently, this problem should be applicable (and therefore also the solution) on holder from other manufacturers.
Finally, it should be mentioned that the stand is even for the price of excellent quality. Thus, the product is recommended, at least for one or two side reflectors.