Hello and welcome to our community! Is this your first visit?
Doing it with or without air.
I read your post and thought I'd give my 5p worth as it's almost the same discussion I had not long back, but I've been there, done that and got the V-weights to prove it.
It sounds like you're in a similar situation to myself. If I dive with a stage and my canister torch, I need no lead in freshwater. (twin 12L faber, 2Kg stainless steel OMS backplate).
However, if like at the weekend I'm just going for a bimble, no torch or stage, I need 4Kg on a weight belt.
I bought 2x2Kg V-Weights and a 1Kg one. I did a check dive at Stoney with 4Kg of V-Weights behind the backplate, and found my legs extremely floaty. Way way more than normal. So it made my trim horrific.
Being 6ft2 the movement of the weights from my hips, 6-7 inches higher up my back made a massive difference to my trim.
The following dive I switched out the v-weights, and just used my usual 4Kg of lead on the belt and my trim was spot on. I also use a freediving thick rubber weight belt, with 2x low profile 2Kg weights I got from a french dive shop, rather than a fabric one so it doesn't spin round.
From that day forward my v-weights have been relegated to the garage (so if anyone wants 2 x 2Kg Plastic coated V-Weights, make me an offer! I'm keeping the 1Kg one as I use it on my twin 7's which works quite well when just swapping from 12's to 7's like for like. Strangely I need no belt change - just the extra 1Kg on the v-weight)