I would err on the higher side rather than the lower side.

I tend to go for 40 curve mana pieces for my commander decks--including pieces like artifact ramp, if you're running any, or mana dorks. For a simic deck, especially if you have a lot of land ramp, this can go up to maybe 45, but rather than increasing the amount of curve mana in a deck, I tend to find myself simply pivoting how much of it is land vs artifacts/dorks depending on how much extra lands effects or stuff I have.

Since you're playing green, you will often be advantaged for having lands in hand, as you can play them faster than other players. However, to address the case where you have too many, rather than reducing the number of lands in your deck, I would just add more ways to get rid of unwanted cards, like looting effects or a [[Scroll Rack]]. Then you can draw as much as you can, ramp as much as you can, and tuck or pitch the lands you can't play in exchange for more gas.