I've done more explo than anything else in EvE so far. Somebody on Reddit asked for fitting help today, so I thought I'd share my current fitting idea there as well as here.
I'd always recommend a Helios over an Astero for pirate explo. You'll lose more of them, but they are so much cheaper that IMHO it's never worth the extra risk. It's not like you're going to fight anyhow, and a Helios runs away quite splendidly.
Here's a prototype Helios fit to get started. It has some fitting room, and is one of about a million ways to fit: I went for super-cheap and low-skill fittings here where possible, but I actually use T2 of many of the modules. You could add more tank instead of evasion. An overdrive would be preferable to avoid scramming: the MWD is much more convenient for moving between explo cans, and arguably if your hunter is in scram range you're webbed anyhow.
[Helios, Dual Explo Evade] Warp Core Stabilizer I Damage Control I Inertial Stabilizers I Relic Analyzer II Remote Sensor Dampener I, Scan Resolution Dampening Script Data Analyzer II Type-E Enduring Cargo Scanner 5MN Microwarpdrive I Core Probe Launcher II, Sisters Core Scanner Probe Covert Ops Cloaking Device II Small Gravity Capacitor Upgrade I Small Gravity Capacitor Upgrade I Hobgoblin SD-300 x1