11/10 speed cassette remove 2 cogs to fit 9 speed hubs
This will not work. The sprocket spacing decreases by about 0.5mm as the number of sprockets increases. The difference sounds small but you would get awful shifting and indexing problems at the largest and smallest gears.

BTW:  8, 9 an 10 speed cassettes all fit on the same width freehub body. 11 speed road gets slightly wider. 

You'll have to look for a 9 speed cassette with the large sprockets you want. Beware you will get big jumps between gear ratios which could negate the benefit of the low gear ratios. Opinions expressed on this site about how well Roadlink or other hanger extenders work are varied, 
so don't expect the setup to work well straight away.