To determine the optimal reliance on hybrid bonds in a company's capital structure, we must evaluate the cost and benefits of hybrid capital relative to other sources of funding like senior debt and common equity.

1. **Cost of Capital Analysis**: Hybrid bonds are structurally subordinated to senior debt, meaning they carry a higher risk for investors and thus require a higher yield. The provided market data shows a significant "Sub-sen delta" (the spread between subordinated/hybrid debt and senior debt), which reached 2.295% in 2022. This makes hybrid debt noticeably more expensive than standard senior corporate bonds. 
2. **Tax Shield & Efficiency**: Standard senior debt typically enjoys full tax deductibility on interest payments. While hybrid coupons can sometimes be tax-deductible depending on the jurisdiction and specific bond structure, the financial statements show marginal tax relief on these payments (e.g., just a 13M DKK tax benefit on 529M DKK of hybrid coupon payments in 2022). Therefore, senior debt provides a vastly superior tax shield per unit of cost.
3. **WACC Minimization**: In standard theoretical frameworks (like the Trade-Off Theory or purely mathematical WACC optimization) without imposing external rating agency credit requirements (which typically cap standard debt and give partial equity credit to hybrids), senior debt strictly dominates hybrid debt due to its lower cost and more efficient tax shield. Thus, to minimize WACC, a company should fully exhaust its optimal senior debt capacity before considering equity, leaving no mathematically optimal allocation for hybrid bonds. 

Because standard senior debt is cheaper and offers superior tax efficiency, the optimal theoretical allocation for hybrid bonds in an unconstrained capital structure model is 0%.

<answer>0%</answer>