I guess that there really isn't a cheap and easy solution to the problem and unfortunately I see this situation time after time. Far too many people don't understand the concept or operational parameters on mod-con boilers and as a result an awful lot of them get a bad reputation when 99% of the time it's installation error, not the boiler. It would be the best option if he can return it and go with something substantially better matched to the radiation but again, assuming the baseboard is copper fin tube, most mod cons are not going to match well. I hate advising less efficient equipment but n this case a gas boiler in the high 80's would most likely perform better and cost about the same to operate. Biase with a Carlin EZ power gas burner would be my choice I think.