Reinsulating attic hardline ductwork

1970's cape cod in SW Mo.
Attic space isn't huge but contains the upstairs air handler and ductwork.
In the next couple of weeks I will be ripping out the old insulation on the floor, airsealing, and installing r30 roxul between joists with r30 fiberglass going perpendicular.

The current hardline ductwork - very little box and mainly 6" rigid in an octopus type setup. The 6" is covered (in most places) with the standard yellow fiberglass and easily torn grey plastic-like covering.

First off, any reason to replace the hardline with flexible?

If not, What's the best option for reinsulating the hardline? Trying to resleeve it would be near impossible I think. I was planning to rub mastic over the joints before doing anything.
Tips or suggested products?
I have plenty of 1" xps leftovers but I can't think of a good way to use it to box in the ductwork that makes the work to do so feasible.

 

I'm not a fan of flex ducts in an attic. Hard to support.

There are two types of duct insulation....
One is fiberglass with a foil wrap and foil covered bubble wrap type plastic like Reflectix.

 

Thanks PJmax.
I kind of hate to go to flex also. Granted as far as support goes, these lay directly on the joists so I don't think I'd have a problem there. Plus I could even lay strips of xps under them to bridge the joists so they don't bend over the joists over time. Though the roxul will actually come over the joists a bit so that's a non-issue really.
I don't like the long strips of foil faced fiberglass that you wrap around the duct, overlapping as you go. I tried that before encapsulating my crawlspace and it was a pain to deal with even with plenty of room.
Or maybe I could find some where the strip is wide enough that I lay it out under the duct, then wrap it up with a single seam lengthwise that I tape? That wouldn't be bad.

Though flex with the insulation already in place is appealing...