I've converted two Chipmunks from Gipsy to Lycoming power over time, it does make it a jump in and start aircraft rather than the rigmarole of trying to start a Gipsy Major engine. The downside of course in UK is it now becomes a non aerobatic aircraft. I think if one had asked Dick Stratton, the instigator of the UK mod, if he could have gone the extra mile and gained aerobatic approval, he would have agreed, but the end game was glider towing so the cost wasn't worth it. Whether the Portuguese aircraft are cleared for aeros I no not.