How to shim Americast tub apron?

[JoshinDC]

I'm setting a Americast Cambridge alcove tub, and the subfloor where the apron will rest is about 1/4" lower on the drain side. I know to measure for the ledger from the high point and then to shim the floor, but what do I use to shim it? Since the weight of the tub is on the apron I assume I at least need hardwood shims, but should I push mortar under the apron around the shim? I'm not sure how careful I need to be about concentrating stress in one location on that end of the apron. If I should use mortar, would (modified or unmodified) thinset work? I'll have both on hand for tiling. If not, can you recommend a product?

Also, I was thinking of putting a bead of silicone caulk on the ledger to try and head off any creaking issues. Good or bad idea? I do not plan on placing any mortar bed under the center of the tub, per the installation instructions. I also have kerdifix, but it seems like that has a short open time and I'll be wrestling the tub into the space myself (and it's a reno so I'll have to rotate instead of slide it in.)

Thanks in advance,
Josh

 

[Terry]

Most any door shim will work for that. The tubs pretty much meet the floor now and they suggest some Silicone laid down first for the center portion.
Some mortar or floor grout to fill the gap would work under the apron after setting too.

 

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[JoshinDC]

Thanks Terry!
This one is an inch or so off the floor, so the caulk on the floor won't help anything.

What do you think about silicone on the stringer?

Would thinset be good to shove under the apron, or should I go out and buy something else? Sorry for being dense; I just have 2 things called mortar and one called grout that I've already bought for the tiling project am I'm just wondering if I can avoid another 50lb bag.

Two more questions I thought of:
1) how fragile is the tub? If I stand it on it's drain end and tip into place (like you describe here: https://terrylove.com/forums/index.php?threads/installing-a-kohler-villager-cast-iron-tub.33212/), do I need to worry about damaging the drain-side apron corner (that it would pivot on)?

2) I've seen a few people complain that it's hard to make a seal on the outside of the drain because of imperfections in the composite coating. There's definitely a casting mark on mine that isn't sanded out well. Any reason I shouldn't try and smooth it out with an orbit sander before installing?

Thanks again,
Josh