Probably a silly question, but you can improve armor/weapons via Tempers/Rosin/Wax to improve their stats and it's a per-piece process; what I was wondering was how do item sets with scaling stats/effects work with regards to improvement?

Say the Viper's Sting set:

(2 items) Adds 688 Weapon Critical

(3 items) Adds 967 Max Stamina

(4 items) Adds 688 Weapon Critical

(5 items) Your Melee Attacks deal 8311 Poison damage. This effect can occur once every 4 seconds.

The various item "levels" of the set provide different effects, so my silly question was to improve a set's effects do you have to improve the number of set items appropriately? For example to boost Viper's 5-set bonus, do I have to improve all 5 pieces to reach that point or does only a certain % of the set have to be improved to consider it all improved?

Assuming a full purple Viper's set, say I gold 2 items: my understanding is I'll have a gold value on the 2-item set bonus (Weapon Crit) and the 3-item and above bonuses will remain purple values: if I improve a 3rd set item, the Max Stamina bonus will become gold value and the 4 and 5-item set bonuses will still be purple and so on.

Is that a correct understanding, or are there shortcuts where you don't have to improve all set items but can get all set item bonuses maxed out?