I use the stock Fender 7250 NPS strings - but on this bass only!
The Jag just loves these strings, by whomever they were made, in whatever country and by whatever method. I don't care if they were wrapped around a stick in the back yard of a mud hut in Ethiopia, they are just great!
Just remember that Fender says their OE strings are ALL 7250 NPSs. They are NOT! They are all over the board for quality and musical/physical playability and not even the same 7250s of a year ago.
I personally feel that changing the bridge to a Hi-Mass would kill a lot of the tonal quality and resonance that the Jag is known for in it's original hardware.
Since the bridge is a portal to the tone-eating wood of the body, sending the lows to the black hole would be a big mistake.
Most everyone who swears about the positive value of a H/M bridge, says they have improved the slap and pop capacity of their bass - and therein lies the truth: the lows are diminished by a quantum amount and that's not where I would want to go.
They DO look cool however, and there's no debating that - at least to me. I, however, refrain from taking the voice I like and messing with it for just something that looks cool.
Kinda like putting a blower scoop on a Cadillac CTS.