FOOL AROUND = synonyms for FOOL "wrapped around" phrases. CHEST BUMP is a colorful base phrase — neat that CH/UMP happens to be wrapped around it. And I thought the juxtaposition of MOTOR NEURON and MORON was particularly amusing, the latter not using a ton of the former.

I wasn't as taken with DORK around DOUBLE PARK. The dictionary definition is "a dull, slow-witted, or socially inept person," but I'm more used to (and partial to) DORK as a compliment, as in "that dorky girl has some serious nerd cred!" Perhaps this explains a lot about me.
DUNCAN PHYFE … whoo, that was a toughie to put together. Thankfully Lynn took her usual care to make all the crossings gettable. I did struggle with the SNIFF AT crossing, but mostly because that PHYFE last name looked so odd. I was curious if any other phrases were available for DUNCE — one I liked was the DEAD CAT BOUNCE, an investing term related to a technical chart pattern. Usually I'd prefer to stay away from nasty-sounding terms, especially ones referring to death, but given that DEATH is already in the grid …
DUE DILIGENCE could have worked too.
Not that DUNCAN PHYFE is bad, but it sure is tough for a Monday and may not do much for non-furniture enthusiasts like myself. I did appreciate that the clue was interesting enough that it made me want to look him up.
I did find it un-Lympelian to get an assortment of crossword glue: CSA, ATA, ASSN, ISR, ENGR, ETTE, and especially SERE. Thankfully it was spread around the grid so it didn't seem overwhelming in any one spot, but as a whole, it was a good bit more than we usually see in her puzzles.
This type of grid arrangement often does cause construction difficulties, what with those four biggish corners plus the fact that so many regions have to interact with two themers. So I did appreciate Lynn working in some nice mid-length fill such as ID SAY SO, SUMATRA, FERRARI. Pretty good use of those 7-letter slots, helping to make up for some of the gluey bits.