Opera uses chromium, which makes using both opera and chrome UA strings unnecessary. Also OS version doesn't matter really, I used 6.3 since even when I had XP and Win7, Win8, and still now in win8.1
and it gets truncated at 185 characters, best to take out the OPR. Safari causes problems, and you really don't need the ; U; part in it, because everything defaults to "U".. and Maxthon should go AFTER Chrome, for it to detect your browser as Chrome and not Maxthon, which is necessary for most sites.
this should work better for compatibility.Mozilla/5.0 (compatible; Windows NT 6.3; WOW64; IA64; en) AppleWebKit/599.0+ (KHTML, like Gecko) Chrome/38.0.2066.0 Maxthon/4.4.2 QupZilla/1.6.6and if you want it fully UNtruncated, you need to make 4.4.0.4000 into 4.4.0 or 4.4.2
now it's also 144 characters.