Preflop adjustments for ante cash games with mandatory straddles in 4-card PLO.

Hello everyone! I'm new to the PLO forums so please excuse me if I get some of the formatting wrong.

I've been in the process of switching from NLH Cash to PLO cash and I've got a question on a specific format that I've been playing online.

The game I've been attempting to reg is a 1/2 game with mandatory straddles as well as a 0.5bb ante required from all players. The game seems to have a solid base of fish who are playing quite poorly and I've deduced that the game is beatable; however, I'm a bit confused on the type of preflop adjustments I should be making in a game that has mandatory antes and straddles. I feel like I'm playing quite well against the fish but I feel a little lost when trying to battle some of the better regs and pros within the game. As a result I feel that my winrate is much less than what it could be.

How should I be adjusting the amount of hands I'm playing? For reference I currently use a 27%VPIP with 16% PFR. Is this too tight for the amount of pot odds I'm getting with the antes and straddles? Additionally, how should I be varying my opening size for such a game? The open to pot with no other limpers is around 11.5bb and this seems very large when the max buy is 200bb.

Thanks a lot for any advice y'all. Excited to be more active in this forum!