Combine 2 units of HP 1920 or 1950 switch as single logical switch

Hi,

In HP 1920/1950 switch brochure, it shows it can stack up to 4 units. I'd like to know it can be combined to form a single logical switch with at least 2 units or not. I'd like to provide high resilent switch to connect with two NIC(to form a teaming) on server/hypervisor. As I know, the IRF (to form single logical switch) is supported on high-end model such as 5500 series.

Any ideas, please share us.

Thanks.