Wheelchair luggage racks?

I haven't used the Freewheel rack, and I think it has been discontinued.  I read reviews of load making wheelchair feel unbalanced, which seemed credible because the weight was so forward.  The TiLite racks I have used to carry my large and bulky guitar (hardshell) case.  They hold the weight close to you, and I secure the upper part with a fastclip/strap around my body.  Worked well for me for this purpose.  Mine are old version, and not removable easily.  Newer (?) design of ones in link you sent appear to be removable.  This is desirable because they add a bit of weight when lifting chair in and out of car.  Carrying stuff in chair is a challenge!  I regularly use a backpack and underseat bag, which I got at www.activedogs.com--excellent quality and durability.  A Jansport "Unhinged" backpack is also a good value, but harder for me to access behind the chair with RA and paralysis.