"Running out of ailerons at 20 kts xwind? Are you sure we are flying the same 737?"
Excerpted from my admittedly 10 year old 737 NG Flight Crew Training Manual: "Sideslip only (zero crab) landings are not recommended with crosswind components in excess of 17 knots at flaps 15, 20 knots at flaps 30, or 23 knots at flaps 40. This recommendation ensures adequate ground clearance and is based on maintaining adequate control margin."
"That would take a VERY accurate piece of co-ordination."
Boeing advertises three crosswind landing techniques: decrab-during-flare, touchdown in crab, and sideslip. The decrab-during-flare technique does not involve lowering a wing; the intention is to decrab just before touchdown while maintaining wings level. I'm not a four engine guy, but my understanding is that this is not a new idea to the DC-8 crowd. It was required training at my operator before we could utilize the full crosswind capability of the 737 MAX, because of the reduced wingtip clearance.
A particularly useful reference for the topic of crosswind landings is here:
https://reports.nlr.nl/xmlui/bitstre...=1&isAllowed=y