The Upper House has no power, it is not like the US senate, but more like the UK's House of Lords, if not weaker. The fact remains that Harti, which is larger than D&M, have 27 seats compared to 61 for D&M.
This is why Gaas would be an idiot to accept the continuation of this system, it would mean permanent underrepresentation for Harti.
There are more Darod in Garissa county alone than D&M alive.D&M is much larger than Harti. D&M is probably bigger than Hawiye and Darod