A lot of people don't like them because sometimes the shaft can resonate and shoot up and down which causes rapid wear (and it's noisy). To be honest, both our CV's plunge on our car too - and the shaft slides on the splines as well - never had a problem with it, but then I'm not sure we'd notice, given they're doing that anyway - I'm afraid that where the crossover into road stuff dies down a bit

The only thing we do run is some little urethane 'bump stops' almost, in the CV joints themselves, to take out some of the shock if one end of the shaft hits full extension with any force.
I have actually seen a fully floating setup on a front wheel drive FIAT out of the factory - they used a rubber mass damper on the driveshaft to stop the resonance, cheap, light and easy to fit, but it might be trial and error getting the position and size right.
I'd run it and see what happens, I'd say it'll probably be fine, if you do get vibration, or fretting on the circlip (I assume the shaft is circliped in?), then you'll need to have a look at damping it or it'll pull the shaft out at some point. Even something as silly as thicker CV boots might help.