I think the Investment 4bb is very big with a wide range. You can make the pot bigger later on and you avoid super profitable 3bet-spots for the players behind you. 5bb with good hands 4bb with weaker hands is highly exploitable but you can do it if you are in the BB because no got player is behind you to exploit your sizing.

Size depends a bit how bad the player is, I play normal tables and try bigger sizing with better hands against weak players. Okay I dont try to isoraise around 8bb with AA but I try it first time with an okaish hand like KQo, if he calls, I split my range into good hands 8bb (all strong TPTK-Hands and high pocketspairs) and nice hands with normal sizing (all hands you think isoraise > check).

You only should do that in the BB or if weak players or nits are behind you.