Yes, thousands of people fly long-hual in economy everyday, and most of passengers are in Y than J, so it is just facts of life.

I think the middle section aisle/middle seats combination works best. Cross aisle seatings are subject to having to get up frequently for fellow passengers' bathroom visits.

Some sugest buying a empty middle seat, and I would also like to suggest looking into buying 2 Premium Economy seats factoring in the cost of buying three economy seats. I have seen Premium Economy fares quite competitive (as compare to regulator economy) on certain routes. If one is willing to buy an empty middle seat, then if the cost is the same, I'd buy two Premium Economy.

Also, if one is not tied to "loyalty" to UA, check out some of the Asian based or Middle-Eastern based carriers that may offer competitive PE and Business fares to sometimes pretty high UA Y fares, IMHO.

I did a roundtirp betwwen SIN and US via Istanbul on Turkish in Business (long layover but in an amazing lounge) for about $2.5K just before Covid. Shop around for best deals if you are not tied to frequent "purchase" programs that Airlines disguise them as freqquent flyer programs nowadays.