First time installing maxx vichy corner tub questions

Help!!! I am new to this so please bear with me. I am converting a bedroom to an ensuite master in a 50 year old bungalow. Have removed floor, sistered joists, put down 3/4 ply. Ordered a vichy 5555. Wife wants it 5 inches higher than it will be by resting on floor. I will be building a deck around it and tiling. Question is,,,,how can I raise the height of the subfloor under the tub this much? That would be about 10 sheets of 1/2 ply. Supporting sides is not an issue as I can build the deck to height. Second question is, manufacturer recomends morter bed covered by poly. What mix of morter should I use, how much and how and where do I place it? Last question is if there is a way to raise the subfloor, does this cause plumbing problems with the drain? I won't bore you with my custom shower questions yet. (more to come)

Thanks

Well, I'd probably rip a bunch of 2x6 lumber down, build a box as if it was a floor structure, then top it with 3/4" ply. If you can live with it lower, you could use 2x4's, which would give you just under 4" when topped with 3/4" ply. This would give you some room to run the plumbing, but you'd still have to have a hole in the floor below to have enough room for a p-trap.

Check out www.johnbridge.com for your tilling questions.

bath deck questions

If I raise the tub, are there any issues with the trap that I should be concerned with? The neck from the tub to under the floor would be about 6 inches. Also, do I tile the deck before I put the tub in , or after?