The Wildkat grapple came with 6' long 3/8" lines (I think they are 3/8" anyways). These lines have 1/2" male fittings on them. I was thinking of cutting those fittings off and getting 1/4" MPT ends put on them and putting 1/4" QC on the ends of what is already there. I'm not sure what (if any) fittings from DHH would fit this Parker hose.
Then I was thinking of either just wire tieing those lines to the loader arm or making up some kind of bulkhead. If I did a bulkhead I would use another set of 1/4"QC's were the loader QC fittings are so if I want to take the loader off I could disconnet it there as well. The lines to the rear remotes would remain of the tractor all the time.
1/4 inch or 3/8 inch are fine as far as hydraulic flow. Bigger issue is what adapters you need to get to 1/2 Pioneer fittings commonly used on the FEL side. Of course you could also put 1/4 or 3/8 inch Pioneers on the FEL side too. One benefit of 3/8 over 1/4 hose is that they are a little tougher and would be more likely to survive a snag on brush etc without ripping. Ask me why I know. Still, I wouldn't change anything if you already have it.