No it is not safe, yes I have done it, I finally broke down and bought the correct tool off Ebay to do it. Not the MB tool, a generic, not exactlly the same quality but its price was right, much safer than nothing and it works perfectlly. If you do it without, be careful, it is possible, but i dont recommend that people do it. Very careful.
If they are broke, it might be ok with less pressure, it there is still the same pressure on them, not any safer. Install will be difficult without the tool, but tnot impossible. I would not relay all this to my wife prior to doing the work, you might not tell yours till after either

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Christopher Henkel
1990 190E 2.6 - Arctic white SOLD
1986 190E-16v - Blauswartze
1993 300CE - SOLD
2003 W208 CLK 320 Cabriolet - Magma Red