They would be fine. Byram isn't small either, he's likely flirting with 6'2 at this point, was 6'1 when he was drafted.
If they felt like it was an issue, they could have just paid to get another "physical" Dman at the trade deadline. Could have had Luke Schen this last deadline for a 3rd for example, arguably a better player then Manson at this point quite frankly. This year, you've got the like of Lyubushkin, Cole, DeMelo, Zadorov, Tanev, Dumba, all of which could easily fill the "Manson role" if they hadn't signed him.
I would much rather be spending assets for depth pieces like that at the trade deadline then doing nothing and continuing to leave one of the most important positions on the team(2C) either completely vacant like last year, or with a huge question mark like RyJo this year.