New Zenner - Having trouble setting up shipping module.

Can I set up shipping for the following scenario?

(a)
Flat rate for 'most' products (below 1.5kg)
Order one item and pay only £3.95
Order two or more items and pay only £3.95

(b)
Flat rate for 'fragile' products (above 1.5kg)
Order one fragile item and pay only £8.95
Order two or more fragile items and pay only £8.95

(c)
Flat rate for 'furniture' products (very large items)
Order one furniture item and pay only £19.95
Order two or more furniture items and pay only £19.95

Ideally would like the greater of the postage rate to be automatically selected if selecting combined items from a,b or c.

Am I on the right track using flat rate with maybe two flat rate clones - But how do I define which products fall into which postage rate?