Amp protection circuit modification & output flyback diodes

[ExtraThiccBoi]

Hi,
i have rebuilt this sweet little amp and it sounds great, managed to fix all factory issues caused by bad construction and wiring. I am still a beginner and i learn as i go.
I am looking for a modification to bring the amplifier up more slower than stock (8s). This is done by this circuit (schematic).
The circuit senses the amplifier output through Q5 and Q6. Diodes D3 and D2 are connected to the AC lines (AC-GND-AC), creating a negative power supply i suppose.
It can short the inputs to ground with JFETs Q401 and Q402. Next, it controls something in the power amp through Q417 (and equivalent in the other channel), i think disables the output section.
The circuit brings the amplifier up slowly, unshorting the inputs and turning on the power section after the 8 or so seconds after the supply voltage is turned on. It also senses the power amp output,
overcurrent and short circuit (load of 2 ohms or less i think) protects the output section. I have been trying to have a crack myself on this, first i thought C11 along R5 and R6 might be creating a time constant. Using rc calculators, 33uF with 222Kohm (680K and 330K in par.), it's around 8s. Then i realized this might not be true and it might have an effect on the protection times and values. What would be the correct component change to increase the time to approx. 10-13 seconds?
My second idea is to add a flyback diodes in the output, like higher-priced amplifiers from HK (more or less the same thing with slightly different components) had. I would like to ask if it's necessary to have them and if they have any negative effect on sound quality. I know from relays that inductors like to push back current and i don't know if this happens with speakers or not, as they're highly reactive load.
Thanks for any help or info!