Hi David,
I have used Helix Floor with a Pedaltrain Classic Pro, but my application is different from most.
On my Pro there is an RMC wah, Mission Volume, and a Wampler Dual Fusion, along with a Pedal Power 2+ underneath that powers everything including Helix.
The angle is fine for the buttons, the on board expression pedal is a little high up (but I don't mind it), and the LCD screen is easily visible, you wont have any problems there.
Having said that I would not buy one to transport the Helix. I have the soft bag version of the Pro and would not put the Helix in that as I reckon the floor version is a bit too tall and could be exposed to impact (the jog wheel! The big screen!). Mine lives permanently on stage at our church and I just bring the Helix to it and plug it in. I can then pick the whole lot up at once and relocate anywhere on stage, which is brilliant, but that's the only reason I use it.
My humble alternative suggestion is a Pelican style plastic gun case with a flat perforated aluminium pedal board (Custom District make one that looks great, or just DIY for your own needs). It would be light, durable, waterproof, have wheels built in, be easy to load, have handles in the all the right places, and stack beside guitar cases neatly. I have been thinking about that setup for my own gear.
However, secure attachment is always the tricky bit for a Helix sized doodad, no matter what board we select...
Bozie
