If you are prepared to adapt it to your needs you can make it work. But should it be like that?
The idea behind this tool is sound enough but its not very well executed. I made a strongback to prevent the cap deforming as the clamps were tightened, I shouldn't have to. The chain provided wouldn't grip my master cylinder reservoir but that's not the fault of the chain, it's as though the reservoir was designed to prevent the use of tools of this design. I did get it to work but it wouldn't give a 100% seal.