Uppababy Mesa infant car seat

Ho

Hi, are there any users (or used in the past with 1st kid) car seat from Uppababy Mesa?

We have purchased it, installed it as per instructions and lucked it w belts. However I find it extremely unsafe at least if belts are used. We even tested it at work (I work for transportation company) and option w belts us definitely out of the question. If you used it, have you purchased any additional adaptor frame to support it more securely?