To determine the appropriate level of hybrid bonds for Italgas S.p.A., we need to analyze its financial profile, capital expenditure needs, and leverage metrics based on the provided 2022 annual report data, and then map these to the hybrid issuance guidelines.

**1. Financial Profile & Leverage Metrics:**
As of December 31, 2022 (2023-01-01), Italgas reports:
- Total Equity: €2,390,570,000
- Total Financial Debt: €6,544,130,000 (Long-term: €6,402,913,000 + Short-term: €142,437,000 - Other noncurrent: €34,000 - Other current: €290,000)
- Reported Leverage (Debt / Equity): ~2.74x (€6.54B / €2.39B)
- Adjusted Leverage (Debt / Total Capital): ~73% (€6.54B / €8.93B)

While the company operates in the regulated utilities sector, which typically supports higher leverage, an adjusted leverage of ~73% represents moderate to significant leverage pressure. Hybrid bonds receiving 50% equity credit under S&P methodology can meaningfully improve adjusted leverage metrics by increasing the adjusted equity base without the full cost of a pure equity issuance.

**2. Capex & Acquisition Pipeline:**
Italgas is undergoing a substantial investment phase. For FY 2022, cash flow from investing activities was -€1,283,826,000, driven heavily by intangible asset purchases (€766,585,000) and investments in consolidation/business units (€874,741,000). This high capex intensity and M&A pipeline indicates a strong need for capital structure optimization to prevent leverage from deteriorating further.

**3. Rating Headroom & Flexibility:**
The company's operating cash flows (€548,169,000) were significantly lower than its investing cash flows, resulting in a free cash flow deficit. This gap requires funding, and adding hybrid bonds provides limited but useful rating flexibility, cushioning the balance sheet against the ongoing heavy investment program. 

**4. Cost of Debt & Market Conditions:**
The 2022 swap curve has shifted significantly higher (5Y at 1.726%), and corporate bond spreads (iBoxx EUR Non-Financial IG) have widened to ~2.30%. Consequently, the cost of issuing a hybrid will increase the current cost of debt, but not to a prohibitive degree that would deter issuance for leverage optimization purposes. 

**Conclusion on Hybrid Issuance:**
Given the moderate leverage optimization rationale, the meaningful improvement that hybrids would bring to adjusted leverage metrics (through equity credit), and the moderately constrained rating headroom due to the high capex/M&A pipeline, a mid-range hybrid issuance is advisable. Italgas does not face transformational or "very high" refinancing needs that would push the rationale to 15%, nor is its profile so strong that 0% or 3.75% would suffice. A 7.5% target of total adjusted capital provides a balanced approach to stabilize the capital structure during this investment cycle.

<answer>7.5%</answer>