I just got a Rancilio Siliva + Rocky.

I also picked up a bottomless portafilter with a triple basket.

At cafe's I typically order single shot americanos & mochas. Given that, I'd like to learn to pull single shots without wasting coffee.

I hear the single shot basket that comes with the Silvia is terrible, so I haven't even tried it. I've been practicing shots with the double basket, but again I've heard negative reviews due to it being shallow & curved. I weight my doses (14g) and all my shots from the double basket end up with an indentation from the screen's screw head.

So my question is... Can I pull a single shot(7g) from the triple basket of my bottomless portafilter? I like the depth & shape of this basket for tamping.

Thanks

If your puck touches the screen, then you might want to down dose, unless your coffee is old and it's the only way to get something good out of it.
You could buy a basket from other makers to fit your portafilter.
Down dosing on a triple basket will not produce the same result as a single basket normal dose

So my question is... Can I pull a single shot(7g) from the triple basket of my bottomless portafilter? I like the depth & shape of this basket for tamping.

No, it will flow as if you forgot to put coffee in the basket, i.e. essentially impossible. A triple basket is TYPICALLY sized for AROUND 21 grams but keep in mind that coffee beans (and thus grounds) vary in density - about +/- 10% from a universal average (if there be such a thing) could be expected.

Your Rancilio double basket that came with the machine should have p/n 40-100-102 stamped on the exterior. This basket has very nice construction although admittedly a little shallow.

Why not just try it and see what happens? And why not just try using the single basket instead of just believing reviews? If you own it, why not. Ultimately it should be your taste that determines if it's good or not. Not what it looks like or what you have read.

Though, if you do find that the included single basket is giving you trouble, I personally suggest the La Marzocco single basket.

For 58mm machines, there is no better single basket, IMHO.

Right tool for the right job. Get a LM single basket. You are not going to pull a single in a triple basket, or a double basket. Baskets are relatively inexpensive and it helps to have a selection of them for optimal dosing.